Optical system, optical apparatus and method for manufacturing the optical system

ABSTRACT

An optical system (ZL(1)) comprises a plurality of lens groups including a first focusing lens group (G2) and a second focusing lens group (G4) that are disposed side by side on an optical axis, and the second focusing lens group (G4) is disposed at a position closer to an image surface than the first focusing lens group (G2). The first focusing lens group (G2) has positive refractive power, and moves toward an object along the optical axis from focusing on an infinite-distance object to focusing on a short-distance object. The second focusing lens group (G4) moves toward the image surface along the optical axis from focusing on the infinite-distance object to focusing on the short-distance object. The optical system (ZL(1)) satisfies the following conditional expression. −020&lt;βF1/βF2&lt;0.50 where βF1 is the lateral magnification of the first focusing lens group at the time of focusing on the infinite-distance object, and βF2 is the lateral magnification of the second focusing lens group at the time of focusing on the infinite-distance object.

TECHNICAL FIELD

The present invention relates to an optical system, an opticalapparatus, and a method for manufacturing the optical system.

TECHNICAL BACKGROUND

Optical apparatuses such as digital still cameras, film cameras, andvideo cameras have had problems in miniaturization of optical systemsand suppression of various aberrations (see, for example, Patentliterature 1).

PRIOR ARTS LIST Patent Document

-   Patent literature 1: Japanese Laid-Open Patent Publication No.    2011-180218(A)

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention proposes anoptical system described below and an optical apparatus in which theoptical system is installed.

An optical system according to the present invention consists of aplurality of lens groups including a first focusing lens group and asecond focusing lens group which are arranged along an optical axis, andthe second focusing lens group is provided at a position closer to animage surface than the first focusing lens group. The first focusinglens group has positive refractive power and moves in a direction to anobject along the optical axis upon focusing on from an infinity objectto a short distant object, and the second focusing lens group moves in adirection to an image surface along the optical axis upon focusing onfrom an infinity object to a short distant object. The followingconditional expression is satisfied:−0.20<βF1/βF2<0.50,

where

βF1: a lateral magnification of the first focusing lens group uponfocusing on the infinity object, and

βF2: a lateral magnification of the second focusing lens group uponfocusing on the infinity object.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a lens configuration of an optical systemaccording to Example 1;

FIGS. 2A and 2B are diagrams of various aberrations of the opticalsystem according to the Example 1, where FIG. 2A shows variousaberrations upon focusing on an infinity object, and FIG. 2B showsvarious aberrations upon focusing on a short distant object;

FIG. 3 is a diagram showing a lens configuration of an optical systemaccording to Example 2;

FIGS. 4A and 4B are diagrams of various aberrations of the opticalsystem according to the Example 2, where FIG. 4A shows variousaberrations upon focusing on an infinity object, and FIG. 4B showsvarious aberrations upon focusing on a short distant object;

FIG. 5 is a diagram showing a lens configuration of an optical systemaccording to Example 3;

FIGS. 6A and 6B are diagrams of various aberrations of the opticalsystem according to the Example 3, where FIG. 6A shows variousaberrations upon focusing on an infinity object, and FIG. 6B showsvarious aberrations upon focusing on a short distant object;

FIG. 7 is a diagram showing a lens configuration of an optical systemaccording to Example 4;

FIGS. 8A and 8B are diagrams of various aberrations of the opticalsystem according to the Example 4, where FIG. 8A shows variousaberrations upon focusing on an infinity object, and FIG. 8B showsvarious aberrations upon focusing on a short distant object;

FIG. 9 is a diagram showing a lens configuration of an optical systemaccording to Example 5;

FIGS. 10A and 10B are diagrams of various aberrations of the opticalsystem according to the Example 5, where FIG. 10A shows variousaberrations upon focusing on an infinity object, and FIG. 10B showsvarious aberrations upon focusing on a short distant object;

FIG. 11 is a diagram showing a lens configuration of an optical systemaccording to Example 6;

FIGS. 12A and 12B are diagrams of various aberrations of the opticalsystem according to the Example 6, where FIG. 12A shows variousaberrations upon focusing on an infinity object, and FIG. 12B showsvarious aberrations upon focusing on a short distant object;

FIG. 13 is a diagram showing a lens configuration of an optical systemaccording to Example 7;

FIGS. 14A and 14B are diagrams of various aberrations of the opticalsystem according to the Example 7, where FIG. 14A shows variousaberrations upon focusing on an infinity object, and FIG. 14B showsvarious aberrations upon focusing on a short distant object;

FIG. 15 is a diagram showing a lens configuration of an optical systemaccording to Example 8;

FIGS. 16A and 16B are diagrams of various aberrations of the opticalsystem according to the Example 8, where FIG. 16A shows variousaberrations upon focusing on an infinity object, and FIG. 16B showsvarious aberrations upon focusing on a short distant object;

FIG. 17 is a diagram showing a configuration of a digital cameraaccording to an embodiment of the optical apparatus; and

FIG. 18 is a flowchart showing a method for manufacturing an opticalsystem.

DESCRIPTION OF THE EMBODIMENTS

A preferred embodiment for carrying out the present invention isdescribed hereunder.

FIG. 17 shows a schematic configuration of a digital camera according toan embodiment of an optical apparatus of the present invention. Adigital camera 1 comprises a main body 2 and an imaging lens 3 that isattachable to and detachable from the main body 2. The main body 2includes an imaging element 4, a main body control part (not shown) forcontrolling the operation of the digital camera, and a liquid crystaloperation screen 5. The imaging lens 3 includes an optical system ZLconsisting of a plurality of lens groups, and a lens position controlmechanism (not shown) for controlling the position of each lens group.The lens position control mechanism includes a sensor for detecting thepositions of the lens groups, a motor for moving the lens groups backand forth along an optical axis, a control circuit for driving themotor, and the like.

Light from a subject is focused on the optical system ZL of the imaginglens 3, and reaches an image surface I of the imaging element 4. Thelight from the subject that has reached the image surface I isphotoelectrically converted by the imaging element 4, and recorded asdigital image data in a memory that is not shown. The digital image datarecorded in the memory is displayed on a liquid crystal screen 5according to a user's operation. Hereinafter, the optical system ZL willbe described in detail.

An optical system according to the embodiment of the present inventionconsists of a plurality of lens groups including a first focusing lensgroup and a second focusing lens group which are arranged along anoptical axis, wherein the second focusing lens group is provided at aposition closer to an image surface than the first focusing lens group,the first focusing lens group has positive refractive power and moves ina direction to an object along the optical axis upon focusing on from aninfinity object to a short distant object, the second focusing lensgroup moves in a direction to the image surface along the optical axisupon focusing on from an infinity object to a short distant object, andthe following conditional expression is satisfied:−0.20<βF1/βF2<0.50  (1),

where

βF1: a lateral magnification of the first focusing lens group uponfocusing on the infinity object, and

βF2: a lateral magnification of the second focusing lens group uponfocusing on the infinity object.

The above conditional expression (1) defines the ratio between thelateral magnifications of the first focusing lens group and the secondfocusing lens group upon focusing on an infinity object. The opticalsystem of the present embodiment achieves reduction in weight andminiaturization of the optical system by performing focusing with thetwo focusing lens groups, and the second focusing lens group plays amain role as a focusing group while the first focusing lens group playsa role as a focusing group and also plays a role of correctingaberrations caused by the movement of the second focusing lens group. Bydefining the balance of the two focusing lens groups so as to satisfythe conditional expression (1), various aberrations such as curvature offield can be excellently corrected, whereby aberration fluctuations thatoccur upon focusing from an infinity object onto a short distant objectcan be effectively suppressed.

Here, it is advantageous that the corresponding value of the conditionalexpression (1) has a large absolute value from only the viewpoint ofsuppressing the movement amount of the focusing lens groups. On theother hand, the optical system of the present embodiment ensures animprovement in the aberration correction function while suppressing themovement amount of the lens groups, and excellently corrects variousaberrations by limiting the range of the corresponding value of theconditional expression (1) so that the corresponding value does notbecome too large. If the corresponding value of the conditionalexpression (1) deviates from a specified numerical range, it becomesdifficult to excellently correct various aberrations, so that it isimpossible to sufficiently obtain the effect of suppressing aberrationfluctuations.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 0.50 of the conditional expression(1) is set to a smaller value, for example, 0.45, 0.40, 0.35, 0.30,0.25, 0.20, 0.18, 0.15, 0.13 or 0.10. Further, a lower limit value −0.20is also set to a larger value, for example, −0.18, −0.15, −0.13 or−0.10, the effect of the present embodiment can be further ensured.

Further, it is preferable that in the above optical system, thefollowing conditional expression (2) is satisfied:−4.50<fF1/fF2<3.00  (2),

where

fF1: a focal length of the first focusing lens group, and

fF2: a focal length of the second focusing lens group.

The above conditional expression (2) defines the ratio between the focallength of the first focusing lens group and the focal length of thesecond focusing lens group. By satisfying the conditional expression(2), the power balance between the first focusing lens group and thesecond focusing lens group becomes a balance in which an aberrationcorrection function is prioritized, and fluctuations in variousaberrations such as curvature of field are effectively suppressed. Ifthe corresponding value of the conditional expression (2) deviates fromthe specified numerical range, it becomes difficult to excellentlycorrect various aberrations, so that it is impossible to sufficientlyobtain the effect of suppressing aberration fluctuations.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 3.00 of the conditional expression(2) is set to a smaller value, for example, 2.80, 2.65, 2.50, 2.45,2.40, 2.35, 2.30, 2.25 or 2.00. A lower limit value −4.50 is also set toa larger value, for example, −4.40, −4.30, −4.20, −4.10, −4.05, −4.00,−3.95, −3.90 or −3.85, whereby the effect of the present embodiment canbe further ensured.

When the second focusing lens group has positive refractive power, inorder to ensure the effect of the present embodiment, it is preferablethat the upper limit value 3.00 of the conditional expression (2) is setto a smaller value, for example, 2.80, 2.65, 2.50, 2.45, 2.40, 2.35,2.30, 2.25 or 2.00. A lower limit value −4.50 is also set to a largervalue, for example, −4.30, −4.00, −3.00, −2.00, −1.00, −0.50, 0.01,0.05, 0.30, 0.50 or 0.80, whereby the effect of the present embodimentcan be further ensured.

When the second focusing lens group has negative refractive power, inorder to ensure the effect of the present embodiment, it is preferablethat the upper limit value 3.00 of the conditional expression (2) is setto a smaller value, for example, 2.80, 2.50, 2.00, 1.50, 1.00, 0.50,0.05, −0.05, −0.10, −0.50, −0.80, −1.00 or −1.20. The lower limit value−4.50 is also set to a larger value, for example, −4.40, −4.30, −4.20,−4.10, −4.05, −4.00, −3.95, −3.90 or −3.85, whereby the effect of thepresent embodiment can be further ensured.

Further, it is preferable that in the above optical system, thefollowing conditional expression (3) is satisfied:0.50<(−MVF1)/MVF2<7.00  (3),

where

MVF1: a movement amount of the first focusing lens group upon focusingfrom the infinity object onto the short distant object, and

MVF2: a movement amount of the second focusing lens group upon focusingfrom the infinity object onto the short distant object, and where themovement amounts MVF1 and MVF2 represent movements in the direction tothe image surface with positive values.

The conditional expression (3) defines the ratio between the movementamount of the first focusing lens group and the movement amount of thesecond focusing lens group upon focusing from an infinity object onto ashort distant object. By satisfying the conditional expression (3),fluctuations in various aberrations such as curvature of field areeffectively suppressed. If the corresponding value of the conditionalexpression (3) deviates from a specified numerical range, it becomesdifficult to excellently correct various aberrations, so that it isimpossible to sufficiently obtain the effect of suppressing aberrationfluctuations.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 7.00 of the conditional expression(3) is set to a smaller value, for example, 6.80, 6.00, 5.00, 4.50,4.00, 3.50, 3.30, 3.00 or 2.85. A lower limit value 0.50 is also set toa larger value, for example, 0.60, 0.70, 0.80, 0.85, 0.90, 0.95, 1.00,1.05 or 1.10, whereby the effect of the present embodiment can befurther ensured.

Further, it is preferable that in the above optical system, thefollowing conditional expression (4) is satisfied:1.30<fF1/f<5.00  (4),

where

fF1: a focal length of the first focusing lens group, and

f: a focal length of the entire optical system.

The conditional expression (4) defines the ratio between the focallength of the first focusing lens group and the focal length of theentire optical system, and shows the power distribution of the firstfocusing lens group in the entire system. By satisfying the conditionalexpression (4), the function of suppressing aberration fluctuationsworks relatively strongly, various aberrations such as curvature offield can be excellently corrected, and the aberration fluctuations canbe effectively suppressed. If the corresponding value of the conditionalexpression (4) deviates from a specified numerical range, it becomesdifficult to excellently correct various aberrations, so that it isimpossible to sufficiently obtain the effect of suppressing aberrationfluctuations.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 5.00 of the conditional expression(4) is set to a smaller value, for example, 4.90, 4.80, 4.70, 4.60,4.50, 4.45, 4.40, 4.35 or 4.30. A lower limit value 1.30 is also set toa larger value, for example, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65,1.70 or 1.73, whereby the effect of the present embodiment can befurther ensured.

Further, it is preferable that in the above optical system, thefollowing conditional expression (5) is satisfied:−2.00<fF2/f<−0.05, or 0.05<fF2/f<3.00  (5),

where

fF2: a focal length of the second focusing lens group, and

f: a focal length of the entire optical system.

The conditional expression (5) defines the ratio between the focallength of the second focusing lens group and the focal length of theentire optical system, and shows the power distribution of the secondfocusing lens group in the entire system. When the focal length of thesecond focusing lens group satisfies the conditional expression (5), itis possible to reduce the movement amount of the second focusing lensgroup in focusing while excellently correcting the aberrations. If thecorresponding value of the conditional expression (5) deviates from aspecified numerical range, it becomes difficult to sufficiently suppressthe aberration fluctuations while suppressing the movement amounts tominiaturize the optical system.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 3.00 of the conditional expression(5) is set to a smaller value, for example, 2.95, 2.90, 2.85, 2.80,2.75, 2.70, 2.65, 2.60, 2.55 or 2.53. A lower limit value −2.00 is alsoset to a larger value, for example, −1.90, −1.80, −1.70, −1.60, −1.55,−1.50, −1.45 or −1.40, whereby the effect of the present embodiment canbe further ensured.

When the second focusing lens group has positive refractive power, inorder to ensure the effect of the present embodiment, it is preferablethat the upper limit value 3.00 of the conditional expression (5) is setto a smaller value, for example, 2.95, 2.90, 2.85, 2.80, 2.75, 2.70,2.65, 2.60, 2.55 or 2.53. The lower limit value −2.00 is also set to alarger value, for example, −1.80, −1.50, −1.00, −0.50, −0.05, 0.05,0.50, 0.80, 1.00, 1.20 or 1.40, whereby the effect of the presentembodiment can be further ensured.

When the second focusing lens group has negative refractive power, inorder to ensure the effect of the present embodiment, it is preferablethat the upper limit value 3.00 of the conditional expression (5) is setto a smaller value, for example, 2.50, 2.00, 1.50, 1.00, 0.50, −0.05,−0.20, −0.50, −0.80, −1.00 or −1.10. The lower limit value −2.00 is alsoset to a larger value, for example, −1.90, −1.80, −1.70, −1.60, −1.55,−1.50, −1.45 or −1.40, whereby the effect of the present embodiment canbe further ensured.

Further, it is preferable that in the above optical system, thefollowing conditional expression (6) is satisfied:−1.80<βF1<0.60  (6),

where

βF1: the lateral magnification of the first focusing lens group uponfocusing on the infinity object.

The conditional expression (6) defines the range of the lateralmagnification of the first focusing lens group upon focusing on aninfinity object. By satisfying the conditional expression (6), it ispossible to suppress fluctuations in various aberrations such asspherical aberration upon focusing from an infinity object onto a shortdistant object.

If the corresponding value of the conditional expression (6) deviatedfrom the specified range, the deflection angle of an epaxial ray oflight increases, so that it becomes difficult to correct the sphericalaberration. Further, when the symmetry for a principal ray of light ispoor, it becomes difficult to correct distortion and coma aberration.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 0.60 of the conditional expression(6) is set to a smaller value, for example, 0.55, 0.50, 0.45, 0.43,0.40, 0.38, 0.35, 0.33, or further 0.31. A lower limit value −1.80 isalso set to a larger value, for example, −1.50, −1.35, −1.00, −0.80,−0.50, −0.25, 0.01, 0.05, or further 0.10, whereby the effect of thepresent embodiment can be further ensured.

Further, it is preferable that in the above optical system, thefollowing conditional expression (7) is satisfied:−0.60<1/βF2<0.70  (7),

where

βF2: the lateral magnification of the second focusing lens group uponfocusing on the infinity object.

The conditional expression (7) defines the range of the lateralmagnification of the second focusing lens group upon focusing on aninfinity object by a reciprocal. When the lateral magnification of thesecond focusing lens group satisfies the conditional expression (7), itis possible to suppress fluctuations in various aberrations such asspherical aberration upon focusing from an infinity object onto a shortdistant object.

If the corresponding value of the conditional expression (7) deviatesfrom a specified range, the deflection angle of an epaxial ray of lightincreases, so that it becomes difficult to correct the sphericalaberration. Further, when the symmetry for a principal ray of light ispoor, it becomes difficult to correct distortion and coma aberration.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 0.70 of the conditional expression(7) is set to a smaller value, for example, 0.65, 0.60, 0.55, 0.50,0.48, 0.45, 0.43, 0.40, 0.38, or further 0.36. A lower limit value −0.60is also set to a larger value, for example, −0.50, −0.40, −0.30, −0.25,−0.10, −0.01, 0.05, or further 0.10, whereby the effect of the presentembodiment can be further ensured.

Further, it is preferable that in the above optical system, thefollowing conditional expression (8) is satisfied:{βF1+(1/βF1)}⁻²<0.250  (8),

where

βF1: the lateral magnification of the first focusing lens group uponfocusing on the infinity object.

The conditional expression (8) defines the range of the lateralmagnification of the first focusing lens group upon focusing on aninfinity object in a style different from that of the conditionalexpression (6). When the lateral magnification of the first focusinglens group satisfies the conditional expression (8), it is possible tosuppress fluctuations in various aberrations such as sphericalaberration upon focusing from an infinity object onto a short distantobject.

If the corresponding value of the conditional expression (8) deviatesfrom a specified range, the deflection angle of an epaxial ray of lightincreases, so that it becomes difficult to correct the sphericalaberration. Further, when the symmetry for a principal ray of light ispoor, it becomes difficult to correct distortion and coma aberration.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 0.250 of the conditional expression(8) is set to a smaller value, for example, 0.248, 0.245, 0.243, 0.240,0.238, 0.235, 0.220, 0.200, 0.180, 0.150, or further 0.100.

Further, it is preferable that in the above optical system, thefollowing conditional expression (9) is satisfied:{βF2+(1/βF2)}⁻²<0.160  (9),

where

βF2: the lateral magnification of the second focusing lens group uponfocusing on the infinity object.

The conditional expression (9) defines the range of the lateralmagnification of the second focusing lens group upon focusing on aninfinity object in a style different from that of the conditionalexpression (7). When the lateral magnification of the second focusinglens group satisfies the conditional expression (9), it is possible tosuppress fluctuations in various aberrations such as sphericalaberration upon focusing from an infinity object onto a short distantobject.

If the corresponding value of the conditional expression (9) deviatesfrom a specified range, the deflection angle of an epaxial ray of lightincreases, so that it becomes difficult to correct the sphericalaberration. Further, when the symmetry for a principal ray of light ispoor, it becomes difficult to correct distortion and coma aberration.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 0.160 of the conditional expression(9) is set to a smaller value, for example, 0.150, 0.130, 0.115, 0.110,or further 0.100.

Further, it is preferable that the above optical system consists of afront lens group including the first focusing lens group, anintermediate lens group, the second focusing lens group, and a rear lensgroup having positive refractive power, which are arranged in this orderclosest to the object, wherein the first focusing lens group is arrangedat a position closest to the image surface in the front lens group.

In the above configuration, incident light to or emitted light from thefirst focusing lens group becomes nearly collimated light, and variousaberrations can be excellently corrected.

Further, it is preferable that the above optical system consists of afront lens group including the first focusing lens group, anintermediate lens group, the second focusing lens group, and a rear lensgroup having positive refractive power, which are arranged in this orderclosest to the object, wherein the intermediate lens group and thesecond focusing lens group have different signs in refractive power.

When both the intermediate lens group and the second focusing lens grouphave positive refractive power, it is difficult for the second focusinglens group to sufficiently suppress the aberration fluctuation as afocusing group. On the other hand, when both the intermediate lens groupand the second focusing lens group have negative refractive power, thisis not preferable because a ray of light that has passed through eachlens group travels so as to diverge and thus the size of the rear lensgroup is large. When any one of the intermediate lens group and thesecond focusing lens group has positive refractive power and the otherhas negative refractive power, it is possible to excellently suppressthe aberration fluctuation upon focusing from an infinity object onto ashort distant object.

Further, it is preferable that the above optical system comprises anintermediate lens group to be arranged between the first focusing lensgroup and the second focusing lens group, wherein the followingconditional expression (10) is satisfied:−8.00<(−fM)/f<2.00  (10),

where

fM: a focal length of the intermediate lens group, and

f: a focal length of the entire optical system.

The intermediate lens group is a lens group to be arranged between thefirst focusing lens group and the second focusing lens group so as to besandwiched by the two focusing lens groups. The conditional expression(10) defines the ratio between the focal length of the intermediate lensgroup and the focal length of the entire optical system, and shows thepower distribution of the intermediate lens group in the entire system.

In the above optical system, a lens group having a large contribution toimage formation is arranged to be closer to the image surface, and alens group having a large contribution to aberration correction isarranged to be closer to the object. By arranging the intermediate lensgroup satisfying the conditional expression (10), the image formation ofthe optical system can be excellently performed, and various aberrationssuch as spherical aberration can be corrected in a well-balanced manneras a whole. If the corresponding value of the conditional expression(10) deviates from a specified numerical range, it becomes difficult toexcellently correct various aberrations, so that it is impossible tosufficiently obtain the effect of suppressing aberration fluctuations.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 2.00 of the conditional expression(10) is set to a smaller value, for example, 1.85, 1.70, 1.60, 1.50,1.40, 1.30, 1.25, 1.20, 1.15 or 1.10. A lower limit value −8.00 is alsoset to a larger value, for example −7.00, −6.00, −5.00, −4.00, −3.00,−2.50 or −2.20, whereby the effect of the present embodiment can befurther ensured.

When the second focusing lens group has positive refractive power, inorder to ensure the effect of the present embodiment, it is preferablethat the upper limit value 2.00 of the conditional expression (10) isset to a smaller value, for example, 1.85, 1.70, 1.60, 1.50, 1.40, 1.30,1.25, 1.20, 1.15 or 1.10. The lower limit value −8.00 is also set to alarger value, for example, −6.00, −3.00, −1.00, −0.05, 0.05, 0.10, 0.30,0.50, 0.70 or 0.80, whereby the effect of the present embodiment can befurther ensured.

When the second focusing lens group has negative refractive power, inorder to ensure the effect of the present embodiment, it is preferablethat the upper limit value 2.00 of the conditional expression (10) isset to a smaller value, for example, 1.85, 1.70, 1.60, 1.50, 1.40, 1.30,1.25, 1.20, 1.15 or 1.10. The lower limit value −8.00 is also set to alarger value, for example, −7.00, −6.00, −5.00, −4.00, −3.00, −2.50 or−2.20, whereby the effect of the present embodiment can be furtherensured.

Further, it is preferable that the above optical system comprises a rearlens group which is arranged on the image surface side of the secondfocusing lens group and has positive refractive power, wherein thefollowing conditional expression (11) is satisfied:0.50<fR/f<3.50  (11),

where

fR: a focal length of the rear lens group, and

f: a focal length of the entire optical system.

The rear lens group also enhances image formation of the optical systemand contributes to correction of aberrations. The conditional expression(11) defines the ratio between the focal length of the rear lens groupand the focal length of the entire system, and shows the powerdistribution of the rear lens group in the entire system. By arrangingthe rear lens group satisfying the conditional expression (11), it ispossible to enhance image formation and correct various aberrations suchas spherical aberration in a well-balanced manner as a whole.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 3.50 of the conditional expression(11) is set to a smaller value, for example, 3.35, 3.20, 3.00, 2.85,2.70, 2.50, 2.40, 2.30, 2.20 or 2.10. A lower limit value 0.50 is alsoset to a larger value, for example, 0.65, 0.80, 0.90, 1.00, 1.05, 1.10,1.15, 1.20, 1.25 or 1.28, whereby the effect of the present embodimentcan be further ensured.

Further, it is preferable that the above optical system comprises a rearlens group which is arranged on the image surface side of the secondfocusing lens group and has positive refractive power, wherein thefollowing conditional expression (12) is satisfied:−2.00<fF2/fR<3.00  (12),

where

fF2: a focal length of the second focusing lens group, and

fR: a focal length of the rear lens group.

The conditional expression (12) defines the ratio between the focallengths of the second focusing lens group and the rear lens group, andshows the power balance between the second focusing lens group and therear lens group. The second focusing lens group and the rear lens groupare balanced with each other so as to satisfy the conditional expression(12), whereby various aberrations such as spherical aberration can becorrected in a well-balanced manner as a whole.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 3.00 of the conditional expression(12) is set to a smaller value, for example, 2.90, 2.80, 2.70, 2.60,2.50, 2.40, 2.30, 2.20 or 2.10. A lower limit value −2.00 is set to alarger value, for example, −1.80, −1.70, −1.60, −1.50, −1.40, −1.30,−1.20 or −1.10, whereby the effect of the present embodiment can befurther ensured.

When the second focusing lens group has positive refractive power, inorder to ensure the effect of the present embodiment, it is preferablethat the upper limit value 3.00 of the conditional expression (12) isset to a smaller value, for example, 2.90, 2.80, 2.70, 2.60, 2.50, 2.40,2.30, 2.20 or 2.10. A lower limit value −2.00 is also set to a largervalue, for example, −1.50, −1.00, −0.50, −0.05, 0.05, 0.10, 0.30, 0.50,0.60 or 0.70, whereby the effect of the present embodiment can befurther ensured.

When the second focusing lens group has negative refractive power, inorder to ensure the effect of the present embodiment, it is preferablethat the upper limit value 3.00 of the conditional expression (12) isset to a smaller value, for example, 2.90, 2.80, 2.70, 2.60, 2.50, 2.40,2.30, 2.20 or 2.10. A lower limit value −2.00 is also set to a largervalue, for example, −1.80, −1.70, −1.60, −1.50, −1.40, −1.30, −1.20 or−1.10, whereby the effect of the present embodiment can be furtherensured.

Further, it is preferable that in the above optical system, a lensarranged at a position closest to the object is a negative meniscuslens.

By arranging a lens having negative refractive power at the positionclosest to the object, spherical aberration and curvature of field canbe excellently corrected, and by using a negative meniscus lens for thelens, the deflection angle of a ray of light can be made gentle evenwhen the lens has a wide angle of view or a large aperture, and a brightimage with appropriate resolution can be obtained.

Further, it is preferable that the above optical system comprises anintermediate lens group to be arranged between the first focusing lensgroup and the second focusing lens group, wherein the intermediate lensgroup is configured so that at least one air lens having positiverefractive power is formed, and the following conditional expression(13) is satisfied:0.10<−(r2Lm+r1Lm)/(r2Lm−r1Lm)<1.20  (13),

where

r1Lm: a radius of curvature of a surface on an object side of an airlens closest to the image surface among air lenses formed in theintermediate lens group, and

r2Lm: a radius of curvature of a surface on an image surface side of anair lens closest to the image surface among the air lenses formed in theintermediate lens group.

The conditional expression (13) defines the shape factor of the air lensformed in the intermediate lens group. By arranging the lensesconstituting the intermediate lens group so that an air lens having ashape satisfying the conditional expression (13) is formed, variousaberrations such as spherical aberration can be excellently corrected.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 1.20 of the conditional expression(13) is set to a smaller value, for example, 1.15, 1.10, 1.08, 1.05,1.03 or 1.00. A lower limit value 0.10 is also set to a larger value,for example, 0.12, 0.14, 0.15, 0.16, 0.17 or 0.18, whereby the effect ofthe present embodiment can be further ensured.

Further, it is preferable that the above optical system comprises anintermediate lens group to be arranged between the first focusing lensgroup and the second focusing lens group, and the intermediate lensgroup has an aperture stop.

The configuration in which the aperture stop is arranged inside theintermediate lens group, that is, near the center of the optical systemcan minimize flux of light which is away from the optical axis andpasses through the edge of the lens, which is advantageous in terms ofaberration correction. Since the optical system can be configured tohave a shape close to a symmetrical shape, there is also an advantagethat coma aberration can be easily suppressed. Further, the aperturestop is arranged near the focusing lens group that moves upon focusing,so that the movement amount of the focusing lens group with respect tothe aperture stop relatively decreases, which is advantageous in termsof suppressing the fluctuations of aberrations. Furthermore, when theaperture stop is located apart from the focusing lens group, it isnecessary to increase the size of the lens, but the configuration inwhich the aperture stop is arranged between the first focusing lensgroup and the second focusing lens group enables the optical system tobe configured with relatively small lenses, so that the opticalapparatus can be miniaturized.

Further, it is preferable that the above optical system comprises aleading lens group arranged on the object side of the first focusinglens group, and the leading lens group includes a negative meniscuslens, a negative lens, a positive lens, and a positive lens, which arearranged in this order closest to the object. Specifically, it ispreferable that the optical system includes a leading lens group, afirst focusing lens group, an intermediate lens group, a second focusinglens group, and a rear lens group having positive refractive power inthis order closest to the object, and the leading lens group has theabove configuration.

By configuring the leading lens group serving as a correction group asdescribed above, longitudinal chromatic aberration and chromaticaberration of magnification can be effectively corrected.

Further, it is preferable that the above optical system comprises aleading lens group arranged on the object side of the first focusinglens group, wherein the leading lens group includes a negative meniscuslens and a negative lens arranged in this order closest to the object,an air lens is formed between the negative meniscus lens and thenegative lens, and the following conditional expression is satisfied:0<(r2Lp+r1Lp)/(r2Lp−r1Lp)<1.20  (14),

where

r1Lp: a radius of curvature of a surface on the object side of the airlens formed in the leading lens group, and

r2Lp: a radius of curvature of a surface on the image surface side ofthe air lens formed in the leading lens group.

Specifically, it is preferable that the optical system comprises aleading lens group, a first focusing lens group, an intermediate lensgroup, a second focusing lens group, and a rear lens group havingpositive refractive power in this order closest to the object, and theleading lens group has the above configuration.

The conditional expression (14) defines the shape factor of the air lensformed in the leading lens group. The lenses constituting the leadinglens group are arranged so as to form an air lens having a shapesatisfying the conditional expression (14), whereby it is possible toexcellently correct various aberrations such as coma aberration andspherical aberration.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 1.20 of the conditional expression(14) is set to a smaller value, for example, 1.10, 1.00, 0.90, 0.80,0.70, 0.65, 0.60 or 0.55. A lower limit value 0 is also set to a largervalue, for example, 0.03, 0.05, 0.08 or 0.10, whereby the effect of thepresent embodiment can be further ensured.

Further, it is preferable that in the above optical system, the firstfocusing lens group and the second focusing lens group comprise at leastone negative lens. Chromatic aberration can be effectively corrected byproviding a negative lens in the focusing lens group having positiverefractive power.

Further, it is preferable that the above optical system comprises anintermediate lens group arranged between the first focusing lens groupand the second focusing lens group, and the intermediate lens groupincludes at least one positive meniscus lens. The function of thepositive meniscus lens can effectively correct chromatic aberration andcoma aberration.

Further, it is preferable that the above optical system consists of aleading lens group, a first focusing lens group, an intermediate lensgroup, a second focusing lens group, and a rear lens group havingpositive refractive power, which are arranged in this order closest tothe object, and at least one of the leading lens group, the intermediatelens group, and the rear lens group comprises a pair of negative lensesbeing adjacent with each other.

In a configuration in which the pair of negative lenses are provided,the effect of suppressing coma aberration can be particularly expected.A configuration in which an adjacent negative lens is provided to theintermediate lens group and a configuration in which an adjacentnegative lens is provided to the rear lens group can be expected to havean effect of suppressing spherical aberration and coma aberration.

Further, it is preferable that in the above optical system, thefollowing conditional expression (15) is satisfied:1.00<NAm/NAi<1.50  (15),

where

NAi: a numerical aperture on the image side upon focusing on theinfinity object, and

NAm: a numerical aperture on the image side upon focusing on the shortdistant object.

The conditional expression (15) defines the ratio between the numericalaperture on the image side upon focusing on an infinity object and thenumerical aperture on the image side upon focusing on a short distantobject. By satisfying the conditional expression (15), it becomes easyto focus light from a subject at a short distance, and a bright imagewith an appropriate resolution can be obtained by a short-distanceshooting.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 1.20 of the conditional expression(15) is set to a smaller value, for example, 1.19, 1.18, 1.17 or 1.15. Alower limit value 0.10 is also set to a larger value, for example, 0.30,0.50, 0.70, 0.80, 0.90 or 1.00, whereby the effect of the presentembodiment can be further ensured.

Further, it is preferable that in the above optical system, a lensarranged at a position closest to the object among lenses constitutingthe first focusing lens group is a negative lens, and the followingconditional expression (16) is satisfied:1.50<(r2L1+r1L1)/(r2L1−r1L1)<3.50  (16),where

r1L1: a radius of curvature of a surface on the object side of thenegative lens, and

r2L1: a radius of curvature of a surface on the image surface side ofthe negative lens.

The conditional expression (16) defines the shape factor of the abovenegative lens. A negative lens having a shape satisfying the conditionalexpression (16) is provided in the first focusing lens group havingpositive refractive power, whereby various aberrations such as chromaticaberration can be excellently corrected.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 3.50 of the conditional expression(16) is set to a smaller value, for example, 3.30, 3.15, 3.00, 2.90,2.80, 2.70 or 2.60. A lower limit value −2.00 is also set to a largervalue such as −1.50, −1.00, −0.50, −0.10, 0.10, 0.50, 1.00, 1.30, 1.50,1.80, 2.00 or 2.10, whereby the effect of the present embodiment can befurther ensured.

Further, it is preferable that the above optical system comprises a rearlens group which is arranged on the image surface side of the secondfocusing lens group and has positive refractive power, wherein the rearlens group is configured to form an air lens, and the followingconditional expression (17) is satisfied:0.00<(r2Lr+r1Lr)/(r2Lr−r1Lr)<1.20  (17),

where

r1Lr: a radius of curvature of a surface on the object side of the airlens formed in the rear lens group, and

r2Lr: a radius of curvature of a surface on the image surface side ofthe air lens formed in the rear lens group.

The conditional expression (17) defines the shape factor of the air lensformed in the rear lens group. The lenses constituting the rear lensgroup are arranged so as to form an air lens having a shape satisfyingthe conditional equation (17), whereby various aberrations such asspherical aberration and coma aberration can be excellently corrected.

In order to ensure the effect of the present embodiment, it ispreferable that an upper limit value 1.20 of the conditional expression(17) is set to a smaller value, for example, 1.15, 1.10, 1.08, 1.05,1.03, 1.00 or 0.95. A lower limit value 0.00 is also set to a largervalue, for example, 0.03, 0.05, 0.08, 0.10, 0.11 or 0.12, whereby theeffect of the present embodiment can be further ensured.

Further, by adopting the above-mentioned configuration, the followingconditional expression (18) can be satisfied while the above opticalsystem excellently suppresses aberration fluctuations upon focusing:25.00°<2ω<75.00°  (18),

where

2ω: a total angle of view of the optical system.

In the above configuration, by narrowing the range of the correspondingvalues of each conditional expression, a lower limit value of theconditional expression (18) can also be set to a larger value, forexample, 30.00°, 35.00°, 40.00°, 43.00°, 48.00°, 55.00°, 60.00°.Further, an upper limit value of the conditional expression (18) canalso be set to a smaller value, for example, 73.00°, 70.00°, 68.00°,66.50°.

Further, it is preferable that in the above optical system, thefollowing conditional expression (19) is satisfied:0.10<BFa/f<0.75  (19),

where

BFa: a back focus (air equivalent length) of the optical system, and

f: a focal length of the entire optical system.

The conditional expression (19) defines the ratio between the back focusof the optical system and the focal length of the entire system. Bysatisfying this conditional expression (19), various aberrations such ascoma aberration can be effectively corrected.

When the corresponding value of the conditional expression (19) exceedsan upper limit value 0.75, the back focus increases with respect to thefocal length, and it becomes difficult to correct various aberrationssuch as coma aberration. In order to ensure the effect of the presentembodiment, it is preferable that the upper limit value 0.75 of theconditional expression (19) is set to a smaller value, for example,0.73, 0.70, 0.65, 0.60, 0.55, 0.50, 0.48 or 0.45.

On the other hand, when the corresponding value of the conditionalexpression (19) is less than the lower limit value 0.10, the back focusdecreases with respect to the focal length, and it becomes difficult tocorrect various aberrations such as coma aberration. In order to ensurethe effect of the present embodiment, it is preferable that the lowerlimit value of the conditional expression (19) is set to a larger value,for example, 0.15, 0.20, 0.25 or 0.28.

Subsequently, a method for manufacturing the above-described opticalsystem will be outlined with reference to FIG. 18 . A method formanufacturing an optical system comprises configuring each of aplurality of lens groups including a first focusing lens group and asecond focusing lens group (ST1), and arranging the configured lensgroups in a lens barrel under the following condition (ST2): the firstfocusing lens group and the second focusing lens group are arrangedalong an optical axis; the second focusing lens group is provided at aposition closer to an image surface than the first focusing lens group;the first focusing lens group has positive refractive power and moves ina direction to an object along the optical axis upon focusing on from aninfinity object to a short distant object; the second focusing lensgroup moves in a direction to an image surface along the optical axisupon focusing on from an infinity object to a short distant object; andthe first focusing lens group and the second focusing lens group satisfythe above-described conditional expression (1).

The optical system manufactured by the above procedure and an opticalapparatus in which the above-described optical system is installed canachieve high-speed and quiet autofocus without increasing the size ofthe lens barrel, and can also excellently suppress aberrationfluctuations upon focusing from an infinity object onto a short distantobject.

EXAMPLES

Hereinafter, the above optical system will be further described withreference to eight numerical examples of Example 1 to Example 8. First,how to read the figures and tables referred to in the description ofeach example will be described.

FIG. 1 , FIG. 3 , FIG. 5 , FIG. 7 , FIG. 9 , FIG. 11 , FIG. 13 , andFIG. 15 show the arrangement of the lens groups of the optical system ineach example by a cross-sectional view. In the upper part of eachfigure, the movement locus (movement direction and amount of movement)of the focusing lens groups upon focusing from an infinity object onto ashort distant object is shown by arrows with characters “focus” and“cc”.

In FIG. 1 , FIG. 3 , FIG. 5 , FIG. 7 , FIG. 9 , FIG. 11 , FIG. 13 , andFIG. 15 , each lens group is represented by a combination of referencecharacter G and a numeral, and each lens is represented by a combinationof reference character L and a numeral. In this specification, in orderto prevent complication due to an increase in the number of referencesigns, numbering is performed for each example. Therefore, thecombination of the same reference signs and numeral may be used for aplurality of examples, but this does not mean that the configurationsindicated by the combination of the same reference signs and numeral arethe same.

FIGS. 2A and 2B, FIGS. 4A and 4B, FIGS. 6A and 6B, FIGS. 8A and 8B,FIGS. 10A and 10B, FIGS. 12A and 12B, FIGS. 14A and 14B, and FIGS. 16Aand 16B are diagrams showing various aberrations in the optical systemof the respective examples, where FIG. 2A to FIG. 16A show variousaberrations upon focusing on an infinity object, and FIG. 2B to FIG. 16Bshow various aberrations upon focusing on a short distant object. Inthese figures, FNO represents F number, NA represents numericalaperture, and Y represents image height. The value of the F number ornumerical aperture corresponding to a maximum aperture is shown in aspherical aberration diagram, the maximum value of image height is shownin an astigmatism diagram and a distortion diagram, and the value ofeach image height is shown in a lateral aberration diagram. Further, drepresents d-line (λ=587.6 nm), and g represents g-line (λ=435.8 nm). Inthe astigmatism diagram, a solid line shows a sagittal image surface,and a broken line shows a meridional image surface. The distortiondiagram shows the distortion aberration based on the d-line, and thediagram of chromatic aberration of magnification shows the chromaticaberration of magnification based on the g-line.

Subsequently, tables used for describing each example will be described.In tables of [General Data], f represents the focal length of the entirelens system, FNO represents F number, 2ω represents the angle of view(unit is ° (degree), and w represents the half angle of view), and Yrepresents the maximum image height. TL represents the distance obtainedby adding BF to the distance from a lens frontmost surface to a lensfinal surface on the optical axis upon focusing on an infinity object,BF represents the back focus from the lens final surface to the imagesurface I on the optical axis upon focusing on an infinity object, andBFa represents the air equivalent distance of BF.

In tables of [Lens Data], the surface number represents the order of theoptical surface from the object side along the traveling direction ofthe ray of light, R represents the radius of curvature of each opticalsurface (represented by a positive value for a surface whose center ofcurvature is located on the image surface side), D represents thesurface distance which is a distance on the optical axis from eachoptical surface to the next optical surface (or image surface), ndrepresents the refractive index of the material of the optical memberwith respect to d-line, and νd represents the Abbe number of thematerial of the optical member with respect to d-line. S represents anaperture stop, and “∞” of the radius of curvature represents a flatsurface or an aperture. The description of the refractive index nd ofair=1.00000 is omitted. When the lens surface is aspherical, the surfacenumber is marked with * to indicate the paraxial radius of curvature inthe column of the radius of curvature R.

In tables of [Aspherical Surface Data], for the aspherical surface shownin the [Lens Data], the shape of the aspherical surface is representedby the following expression (A). X(y) represents the distance (sagamount) along the optical axis direction from a tangent plane at theapex of the aspherical surface to a position on the aspherical surfaceat the height y, R represents the radius of curvature of a referencespherical surface (paraxial radius of curvature), κ represents a conicconstant, and Ai represents an i-th order aspherical coefficient. “E-n”represents “x10-n”. For example, 1.234E-05=1.234×10-5. A second-orderaspherical coefficient A2 is equal to 0, and the description thereof isomitted.X(y)=(y2/R)/{1+(1−κ×y2/R2)½}+A4×y4+A6×y6+A8×y8+A10×y10+A12×y12  (A)

[Lens Group Data] tables show a first surface (a surface closest to theobject), a focal length, a magnification upon focusing on infinity, anda magnification upon focusing on a short distant object for each lensgroup.

[Variable Distance Data] tables show a surface distance at a surfacenumber at which the surface distance is indicated as “variable” in thetable of [Lens Data]. The left column indicates the focal length and thesurface distance upon focusing on an infinity object, and the rightcolumn indicates the lateral magnification and the surface distance uponfocusing on a short distant object.

[Air Lens Data] tables show the radius of curvature and the value of theshape factor of each lens constituent surface for the air lens formed ineach of the intermediate lens group and the leading lens group.

[Conditional Expression Corresponding value] tables show valuescorresponding to the respective conditional expressions.

Since “mm” is generally used as units of the focal length f, the radiusof curvature R, the surface distance D, and other lengths, the unit oflength is set to “mm” in each table of the present specification.However, the unit of length is not necessarily limited to “mm” becauseequivalent optical performance can be obtained even if the opticalsystem is proportionally enlarged or contracted.

The descriptions of the figures and tables so far are common to all theexamples, and the duplicated descriptions are omitted below.

Example 1

Example 1 will be described with reference to FIG. 1 , FIGS. 2A and 2B,and Table 1.

FIG. 1 is a diagram showing a lens configuration of an optical systemaccording to Example 1. A variable power optical system ZL(1) accordingto the Example 1 comprises a first lens group G1 (leading lens group)having negative refractive power, a second lens group G2 (first focusinglens group) having positive refractive power, a third lens group G3(intermediate lens group) having negative refractive power, an aperturestop S arranged in the third lens group G3, a fourth lens group G4(second focusing lens group) having positive refractive power, and afifth lens group G5 (rear lens group) having positive refractive power,which are arranged in order from the object side.

The positions of the first lens group G1, the third lens group G3, andthe fifth lens group G5 are fixed, and the second lens group G2 and thefourth lens group G4 are arranged so as to be movable along an opticalaxis. Upon focusing from infinity onto a short distance, the second lensgroup G2 moves in a direction to an object, and the fourth lens group G4moves in a direction to an image surface.

The first lens group G1 comprises a negative meniscus lens L11 having aconvex surface facing an object, a biconcave negative lens L12, apositive meniscus lens L13 having a concave surface facing the object,and a biconvex positive lens L14, which are arranged in order from theobject side.

The second lens group G2 comprises a positive meniscus lens L21 having aconvex surface facing the object.

The third lens group G3 comprises a positive meniscus lens L31 having aconcave surface facing the object, a biconcave negative lens L32, anaperture stop S, a negative meniscus lens L33 having a concave surfacefacing the object, and a negative meniscus lens L34 having a convexsurface facing the object, which are arranged in order from the objectside. The negative meniscus lens L34 has an aspherical surface on theimage surface side.

The fourth lens group G4 comprises a cemented positive lens including abiconvex positive lens L41 and a negative meniscus lens L42 having aconcave surface facing the object, which are arranged in order from theobject side. The negative meniscus lens L42 has an aspherical surface onthe image surface side.

The fifth lens group G5 comprises a biconvex positive lens L51, apositive meniscus lens L52 having a convex surface facing the object, acemented negative lens including a biconvex positive lens L53 and abiconcave negative lens L54, a cemented positive lens including anegative meniscus lens L55 having a convex surface facing the object anda positive meniscus lens L56 having a convex surface facing the object,and a parallel flat plate PP, which are arranged in order from theobject side. The positive lens L53 has an aspherical surface on theobject side. The negative meniscus lens L55 has an aspherical surface onthe object side.

Table 1 shows values of various data on the optical system according tothe Example 1.

TABLE 1 [General Data] f = 34.000 FNo = 1.24 ω = 31.8° Y = 21.7 TL =150.038 BF = 15.474 BFa (Air equivalent length) = 14.929 NAi = 0.3740NAm = 0.4176 [Lens Data] Surface Number R D nd νd Object ∞ Surface 178.45289 1.800 1.65844 50.8 2 31.79555 9.212 3 −100.24254 1.800 1.8080922.7 4 77.08680 2.664 5 −1470.34330 4.336 1.95375 32.3 6 −68.61232 0.2007 278.33482 2.538 1.95375 32.3 8 −284.02217 Variable (D8) 9 72.822543.228 1.95375 32.3 10 232.63870 Variable (D10) 11 −201.17190 3.8811.94594 18.0 12 −58.84216 0.200 13 −79.55028 1.800 1.65412 39.7 1465.13432 4.225 15 S 5.772 16 −43.92965 1.800 1.85026 32.4 17 696.993390.200 18 138.39305 1.800 1.49710 81.5 19* 136.03491 Variable (D19) 2089.83290 12.000 1.75500 52.3 21 −53.66816 1.800 1.80301 25.5 22*−69.76741 Variable (D22) 23 41.08076 12.000 1.43385 95.2 24 −1829.481600.200 25 35.60849 12.000 1.43385 95.2 26 335.75250 3.116 27* 69.113588.917 1.74310 49.4 28 −51.12506 1.800 1.75520 27.6 29 35.57211 2.646 30*47.43881 4.336 1.76544 46.8 31 21.88490 12.000 1.59270 35.3 32 86.3826112.874 33 0 1.600 1.51680 64.1 34 0 (D34) Image ∞ Surface [AsphericalSurface Data] 19th Surface K = 1.0000 A4 = −4.21544E−06, A6 =3.77109E−09, A8 = −1.73426E−12, A10 = 1.76549E−16 22nd Surface K =1.0000 A4 = 1.55287E−06, A6 = −1.51154E−10, A8 = −6.16779E−14, A10 =1.65432E−16 27th Surface K = 1.0000 A4 = −2.88315E−06, A6 =−6.70603E−09, A8 = −1.14021E−12, A10 = 5.52111E−15 30th Surface K =1.0000 A4 = −1.09981E−05, A6 = 2.21376E−10, A8 = −1.96393E−11, A10 =7.87337E−15 [Lens Group Data] Magni- Magni- fication First Focalfication (Short- Group surface length (Infinity) distance) 1 1 −144.52 00.52462 2 9 110.06 −1.29515 −40.50152 3 11 −34.37 −0.16996 −0.00762 4 2054.58 13.12918 13.23197 5 23 49.64 −0.08140 −0.08140 [Variable DistanceData] Infinity Short-distance f = 34.000 β = −0.1744 D0 ∞ 149.970 D87.443 1.000 D10 3.240 9.683 D19 1.000 6.611 D22 6.611 1.000 D34 1.0001.000[Air Lens Data]Air Convex Lens in the Intermediate Lens Group

R1=65.13432 (14th Surface), R2=−43.92965 (16th Surface), ShapeFactor=−0.194424153

Air Convex Lens in the Leading Lens Group

R1=31.79555 (2nd Surface), R2=−100.24254 (3rd Surface), ShapeFactor=0.518388217

FIGS. 2A and 2B show various aberration values of the optical systemaccording to the Example 1 upon focusing on an infinity object and uponfocusing on a short distant object, respectively. From the respectiveaberration diagrams, it can be seen that the optical system according tothe Example 1 excellently corrects various aberrations and has excellentimage formation performance.

Example 2

Example 2 will be described with reference to FIG. 3 FIGS. 4A and 4B,and Table 2.

FIG. 3 is a diagram showing a lens configuration of an optical systemaccording to Example 2. A variable power optical system ZL (2) accordingto the Example 2 comprises a first lens group G1 (leading lens group)having positive refractive power, a second lens group G2 (first focusinglens group) having positive refractive power, a third lens group G3(intermediate lens group) having negative refractive power, an aperturestop S arranged in the third lens group G3, a fourth lens group G4(second focusing lens group) having positive refractive power, and afifth lens group G5 (rear lens group) having positive refractive power,which are arranged in order from the object side.

The positions of the first lens group G1, the third lens group G3, andthe fifth lens group G5 are fixed, and the second lens group G2 and thefourth lens group G4 are arranged so as to be movable along an opticalaxis. Upon focusing from infinity onto a short distance, the second lensgroup G2 moves in a direction to an object, and the fourth lens group G4moves in a direction to an image surface.

The first lens group G1 comprises a negative meniscus lens L11 having aconvex surface facing the object, a negative meniscus lens L12 having aconcave surface facing the object, a biconvex positive lens L13, and abiconvex positive lens L14, which are arranged in order from the objectside.

The second lens group G2 comprises a negative meniscus lens L21 having aconcave surface facing the object, and a biconvex positive lens L22,which are arranged in order from the object side. The negative meniscuslens L21 has an aspherical surface on the image surface side.

The third lens group G3 comprises a cemented negative lens including apositive meniscus lens L31 having a concave surface facing the objectand a biconcave negative lens L32, an aperture stop S, and a biconcavenegative lens L33, which are arranged in order from the object side. Thenegative lens L33 has an aspherical surface on the object side.

The fourth lens group G4 comprises a biconvex positive lens L41, and abiconcave negative lens L42, which are arranged in order from the objectside. The positive lens L41 has an aspherical surface on the imagesurface side.

The fifth lens group G5 comprises a biconvex positive lens L51, abiconvex positive lens L52, a cemented negative lens including apositive meniscus lens L53 having a convex surface facing the object anda negative meniscus lens L54 having a convex surface facing the object,a cemented negative lens including a negative meniscus lens L55 having aconcave surface facing the object and a positive meniscus lens L56having a concave surface facing the object, and a parallel flat platePP, which are arranged in order from the object side. The positivemeniscus lens L56 has an aspherical surface on the image surface side.

Table 2 shows values of various data on the optical system according tothe Example 2.

TABLE 2 [General Data] f = 34.000 FNo = 1.43 ω = 32.3° Y = 21.7 TL =125.037 BF = 14.695 BFa (Air equivalent length) = 14.150 NAi = 0.3301NAm = 0.3484 [Lens Data] Surface Number R D nd νd Object ∞ Surface 11000 1.800 1.59319 67.9 2 29.24499 13.130 3 −37.28850 4.069 1.51823 58.84 −93.86687 0.200 5 642.57258 4.931 1.59319 67.9 6 −69.30966 0.200 795.77502 7.486 1.59319 67.9 8 −59.97313 Variable (D8) 9 −54.97475 1.8001.80301 25.5 10* −104.11669 0.200 11 69.48619 10.763 1.59349 67.0 12−48.30276 Variable (D12) 13 −57.29363 2.075 1.94594 18.0 14 −44.389681.800 1.73800 32.3 15 9491.38110 1.515 16 S 3.617 17* −44.64528 1.8001.69343 53.3 18 122.92211 Variable (D18) 19 165.32448 3.998 1.85108 40.120* −53.29124 0.200 21 −82.65344 1.800 1.61266 44.5 22 323.52744Variable (D22) 23 167.52953 3.404 1.88300 40.7 24 −143.67029 0.200 2539.56339 8.526 1.49782 82.6 26 −60.08036 0.200 27 29.78264 4.998 1.4978282.6 28 65.45522 1.800 1.75520 27.6 29 22.67864 11.518 30 −26.842321.800 1.84666 23.8 31 −63.50151 1.857 1.85108 40.1 32* −36.52497 12.09533 0 1.600 1.51680 64.1 34 0 (D34) Image ∞ Surface [Aspherical SurfaceData] 10th Surface K = 1.0000 A4 = 2.49384E−06, A6 = 2.22548E−09, A8 =−1.51167E−12, A10 = 2.82373E−15 17th Surface K = 1.0000 A4 =1.44522E−05, A6 = 2.01672E−09, A8 = −8.69052E−12, A10 = 1.73809E−14 20thSurface K = 1.0000 A4 = 1.03005E−05, A6 = 4.33301E−09, A8 =−4.92005E−12, A10 = 2.23459E−14 32nd Surface K = 1.0000 A4 =8.30658E−06, A6 = 7.24869E−09, A8 = 3.50531E−11, A10 = 6.92136E−14 [LensGroup Data] Magni Magni- fication First Focal fication (Short- Groupsurface length (Infinity) distance) 1 1 129.35 0 −1.22983 2 9 70.320.28696 0.17072 3 13 −28.50 −1.73172 −1.69000 4 19 84.70 121.58232121.55563 5 23 44.22 −0.00435 −0.00435 [Variable Distance Data] InfinityShort-distance f = 34.000 β = −0.1877 D0 ∞ 175.070 D8 9.592 1.825 D121.000 8.767 D18 1.805 2.994 D22 2.259 1.070 D34 1.000 1.000[Air Lens Data]Air Convex Lens in the Intermediate Lens Group

R1=9491.3811 (15th Surface), R2=−44.64528 (14th Surface), ShapeFactor=−0.990636502

Air Convex Lens in the Leading Lens Group

R1=29.24499 (2nd Surface), R2=−37.2885 (3rd Surface), ShapeFactor=0.120894154

FIGS. 4A and 4B show various aberration values of the optical systemaccording to the Example 2 upon focusing on an infinity object and uponfocusing on a short distant object, respectively. From each aberrationdiagram, it can be seen that the optical system according to the Example2 excellently corrects various aberrations and has excellent imageformation performance.

Example 3

Example 3 will be described with reference to FIG. 5 FIGS. 6A and 6B andTable 3.

FIG. 5 is a diagram showing a lens configuration of an optical systemaccording to Example 3. A variable power optical system ZL (3) accordingto the Example 3 comprises a first lens group G1 (leading lens group)having positive refractive power, a second lens group G2 (first focusinglens group) having positive refractive power, a third lens group G3(intermediate lens group) having negative refractive power, an aperturestop S arranged in the third lens group G3, a fourth lens group G4(second focusing lens group) having positive refractive power, and afifth lens group G5 (rear lens group) having positive refractive power,which are arranged in order from the object side.

The positions of the first lens group G1, the third lens group G3, andthe fifth lens group G5 are fixed, and the second lens group G2 and thefourth lens group G4 are arranged so as to be movable along an opticalaxis. Upon focusing from infinity onto a short distance, the second lensgroup G2 moves in a direction to an object, and the fourth lens group G4moves in a direction to an image surface.

The first lens group G1 comprises a negative meniscus lens L11 having aconvex surface facing the object, a biconcave negative lens L12, apositive meniscus lens L13 having a concave surface facing the object,and a biconvex positive lens L14, which are arranged in order from theobject side.

The second lens group G2 comprises a negative meniscus lens L21 having aconcave surface facing the object, and a biconvex positive lens L22,which are arranged in order from the object side.

The third lens group G3 comprises a positive meniscus lens L31 having aconcave surface facing the object, a biconcave negative lens L32, anaperture stop S, and a cemented negative lens including a biconcavenegative lens L33 and a positive meniscus lens L34 having a convexsurface facing the object, which are arranged in order from the objectside. The negative lens L33 has an aspherical surface on the objectside.

The fourth lens group G4 comprises a biconvex positive lens L41. Thepositive lens L41 has an aspherical surface on the image surface side.

The fifth lens group G5 comprises a biconvex positive lens L51, acemented positive lens including a biconvex positive lens L52 and abiconcave negative lens L53, a cemented negative lens including anegative meniscus lens L54 having a concave surface facing the objectand a positive meniscus lens L55 having a concave surface facing theobject, and a parallel flat plate PP, which are arranged in order fromthe object side. The positive lens L52 has an aspherical surface on theobject side. The positive meniscus lens L55 has an aspherical surface onthe image surface side.

Table 3 shows values of various data on the optical system according tothe Example 3.

TABLE 3 [General Data] f = 34.000 FNo = l.83 ω = 32.3° Y = 21.7 TL =125.016 BF = 15.36 BFa (Air equivalent length) = 14.815 NAi = 0.2636 NAm= 0.2869 [Lens Data] Surface Number R D nd νd Object ∞ Surface 139.26923 1.800 1.61272 58.5 2 21.43928 15.946 3 −27.92891 1.800 1.7282528.4 4 140.89907 2.034 5 −202.15932 4.983 1.95375 32.3 6 −45.11074 0.2007 808.08718 7.245 1.77250 49.6 8 −40.13154 Variable (D8) 9 −44.252201.800 1.84666 23.8 10 −64.16132 0.200 11 51.93777 6.937 1.49782 82.6 12−68.38815 Variable (D12) 13 −90.28877 3.400 1.49782 82.6 14 −42.032800.200 15 −71.85728 1.800 1.77250 49.6 16 988.62643 1.590 17 S 3.662 18*−37.29234 1.800 1.69343 53.3 19 38.49299 2.412 1.94594 18.0 20 69.10901Variable (D20) 21 51.49005 4.413 1.49710 81.5 22* −123.19174 Variable(D22) 23 22.03371 7.573 1.49782 82.6 24 −1063.13040 0.200 25* 64.404834.966 1.74310 49.4 26 −38.93018 1.800 1.80000 29.8 27 231.25275 13.14628 −17.57107 1.800 1.84666 23.8 29 −44.05394 1.800 1.59201 67.0 30*−26.89621 12.760 31 0 1.600 1.51680 64.1 32 0 (D32) Image ∞ Surface[Aspherical Surface Data] 18th Surface K = 1.0000 A4 = 8.88687E−06, A6 =−4.33532E−09, A8 = −7. 68001E−11, A10 = 2.47627E−13 22nd Surface K =1.0000 A4 = 5.79541E−07, A6 = 1.75128E−09, A8 = −6.35598E−11, A10 =2.31873E−13 25th Surface K = 1.0000 A4 = −1.22979E−05, A6 = 7.32190E−09,A8 = 6.68548E−12, A10 = 4.98302E−14 30th Surface K = 1.0000 A4 = l.67822E−05, A6 = 3.01627E−08, A8 = 1.09895E−10, A10 = 8.41007E−14 [LensGroup Data] First Focal Magnification Magnification Group surface length(Infinity) (Short-distance) 1 1 146.26 0 −1.43506 2 9 87.95 0.290930.16887 3 13 −30.77 −1.34774 −1.23290 4 21 73.67 −22.67267 −22.62459 523 47.05 0.02615 0.02615 [Variable Distance Data] InfinityShort-distance f = 34.000 β = −0.1768 D0 ∞ 175.030 D8 9.608 1.000 D121.000 9.608 D20 1.000 4.541 D22 4.541 1.000 D32 1.000 1.000[Air Lens Data]Air Convex Lens in the Intermediate Lens Group

R1=988.62643 (16th Surface), R2=−37.29234 (17th Surface), ShapeFactor=−0.927299624

Air Convex Lens in the Leading Lens Group

R1=21.43928 (2nd Surface), R2=−27.92891 (3rd Surface), ShapeFactor=0.131453675

FIGS. 6A and 6B show various aberration values of an optical systemaccording to the Example 3 upon focusing on an infinity object and uponfocusing on a short distant object, respectively. From each aberrationdiagram, it can be seen that the optical system according to the Example3 excellently corrects various aberrations and has excellent imageformation performance.

Example 4

Example 4 will be described with reference to FIG. 7 FIGS. 8A and 8B,and Table 4.

FIG. 7 is a diagram showing a lens configuration of an optical systemaccording to the Example 4. A variable power optical system ZL (4)according to the Example 4 comprises a first lens group G1 (leading lensgroup) having positive refractive power, a second lens group G2 (firstfocusing lens group) having positive refractive power, a third lensgroup G3 (intermediate lens group) having negative refractive power, anaperture stop S arranged in the third lens group G3, a fourth lens groupG4 (second focusing lens group) having positive refractive power, and afifth lens group G5 (rear lens group) having positive refractive power,which are arranged in order from the object side.

The positions of the first lens group G1, the third lens group G3, andthe fifth lens group G5 are fixed, and the second lens group G2 and thefourth lens group G4 are arranged so as to be movable along an opticalaxis. Upon focusing from infinity onto a short distance, the second lensgroup G2 moves in a direction to an object, and the fourth lens group G4moves in a direction to an image surface.

The first lens group G1 comprises a negative meniscus lens L11 having aconvex surface facing the object, a biconcave negative lens L12, apositive meniscus lens L13 having a concave surface facing the object,and a biconvex positive lens L14, which are arranged in order from theobject.

The second lens group G2 comprises a negative meniscus lens L21 having aconcave surface facing the object and a biconvex positive lens L22,which are arranged in order from the object.

The third lens group G3 comprises a positive meniscus lens L31 having aconcave surface facing the object, a biconcave negative lens L32, anaperture stop S, a biconcave negative lens L33, and a positive meniscuslens L34 having a convex surface facing the object, which are arrangedin order from the object. The negative lens L33 has an asphericalsurface on the image surface side.

The fourth lens group G4 comprises a biconvex positive lens L41. Thepositive lens L41 has an aspherical surface on the image surface side.

The fifth lens group G5 comprises a biconvex positive lens L51, acemented negative lens including a biconvex positive lens L52 and abiconcave negative lens L53, a cemented negative lens including anegative meniscus lens L54 having a concave surface facing the objectand a positive meniscus lens L55 having a concave surface facing theobject, and a parallel flat plate PP, which are arranged in order fromthe object side. The positive lens L52 has an aspherical surface on theobject side. The positive meniscus lens L55 has an aspherical surface onthe image surface side.

Table 4 shows values of various data on the optical system according tothe Example 4.

TABLE 4 [General Data] f = 34.000 FNo = l.83 ω = 32.3° Y = 21.7 TL =150.004 BF = 22.354 BFa (Air equivalent length) = 21.809 NAi = 0.2636NAm = 0.3022 [Lens Data] Surface Number R D nd νd Object ∞ Surface 161.45190 1.800 1.60311 60.7 2 24.15620 13.126 3 −30.14784 2.556 1.8466623.8 4 411.13484 1.196 5 −248.37149 6.178 1.84666 23.8 6 −41.33060 0.2007 571.61851 6.861 1.77250 49.6 8 −46.37495 Variable (D8) 9 −47.131562.200 1.84666 23.8 10 −69.78753 0.200 11 75.23248 8.760 1.48749 70.3 12−66.21981 Variable (D12) 13 −86.31055 3.444 1.49782 82.6 14 −41.955820.200 15 −73.08198 1.800 1.77250 49.6 16 95.40664 2.540 17 S 3.766 18−44.98778 1.800 1.69343 53.3 19* 65.01667 0.200 20 59.01722 2.7561.94594 18.0 21 177.88174 Variable (D21) 22 47.31354 8.236 1.49710 81.523* −57.77206 Variable (D23) 24 29.89839 9.302 1.49782 82.6 25−124.65747 0.200 26* 94.01782 7.112 1.74310 49.4 27 −31.94679 12.0001.73800 32.3 28 44.88495 4.885 29 −29.01514 1.800 1.78472 25.6 30−122.38369 2.072 1.74310 49.4 31* −37.12074 19.754 32 0 1.600 1.5168064.1 33 0 (D33) Image ∞ Surface [Aspherical Surface Data] 19th Surface K= 1.0000 A4 = 5.84788E−07, A6 = −4.70258E−10, A8 = 1.13649E−11, A10 =−1.79719E−14 23rd Surface K = 1.0000 A4 = l.61554E−06, A6 = 5.75291E−09,A8 = −1.09239E−11, A10 = 1.27458E−14 26th Surface K = 1.0000 A4 =−5.24945E−06, 1 A6 = 2.78999E−09, A8 = −3.58128E−12, A10 = 2.34155E−1531st Surface K = 1.0000 A4 = 1.59178E−05, A6 = 1.96622E−08, A8 =1.10858E−10, A10 = −1.08461E−13 [Lens Group Data] First FocalMagnification Magnification Group surface length (Infinity)(Short-distance) 1 1 253.20 0 −31.51160 2 9 117.16 0.23631 0.01380 3 13−33.77 −0.67127 −0.53423 4 22 53.72 −4.48399 −4.39324 5 24 70.85 0.188790.18879 [Variable Distance Data] Infinity Short-distance f = 34.000 β =−0.1927 D0 ∞ 150.040 D8 14.584 1.421 D12 1.000 14.163 D21 1.000 5.876D23 5.876 1.000 D33 1.000 1.000[Air Lens Data]Air Convex Lens in the Intermediate Lens Group

R1=95.40664 (16th Surface), R2=−44.98778 (18th Surface), ShapeFactor=−0.359122962

Air Convex Lens in the Leading Lens Group

R1=24.15620 (2nd Surface), R2=−30.14784 (3rd Surface), ShapeFactor=0.110335069

FIGS. 8A and 8B show various aberration values of the optical systemaccording to the Example 4 upon focusing on an infinity object and uponfocusing on a short distant object, respectively. From each aberrationdiagram, it can be seen that the optical system according to the Example4 excellently corrects various aberrations and has excellent imageformation performance.

Example 5

Example 5 will be described with reference to FIG. 9 FIGS. 10A and 10B,and Table 5.

FIG. 9 is a diagram showing a lens configuration of an optical systemaccording to the Example 5. A variable power optical system ZL (5)according to the Example 5 comprises a first lens group G1 havingnegative refractive power, a second lens group G2 (first focusing lensgroup) having positive refractive power, a third lens group G3(intermediate lens group) having positive refractive power, an aperturestop S arranged in the third lens group G3, a fourth lens group G4(second focusing lens group) having negative refractive power, and afifth lens group G5 (rear lens group) having positive refractive power,which are arranged in order from the object side. A front lens groupcomprises the first lens group G1 and the second lens group G2.

The positions of the first lens group G1, the third lens group G3, andthe fifth lens group G5 are fixed, and the second lens group G2 and thefourth lens group G4 are arranged so as to be movable along an opticalaxis. Upon focusing from infinity onto a short distance, the second lensgroup G2 moves in a direction to an object, and the fourth lens group G4moves in a direction to an image surface.

The first lens group G1 comprises a negative meniscus lens L11 having aconvex surface facing the object, a cemented negative lens including anegative meniscus lens L12 having a convex surface facing the object anda positive meniscus lens L13 having a convex surface facing the object,and a cemented negative lens including a biconcave negative lens L14 anda biconvex positive lens L15, which are arranged in order from theobject side.

The second lens group G2 comprises a negative meniscus lens L21 having aconcave surface facing the object, and a biconvex positive lens L22,which are arranged in order from the object side. The negative meniscuslens L21 has an aspherical surface on the image surface side.

The third lens group G3 comprises a positive meniscus lens L31 having aconcave surface facing the object, an aperture stop S, a cementedpositive lens including a biconcave negative lens L32 and a biconvexpositive lens L33, and a biconvex positive lens L34, which are arrangedin order from the object side. The positive lens L33 has an asphericalsurface on the image surface side.

The fourth lens group G4 comprises a biconcave negative lens L41. Thenegative lens L41 has an aspherical surface on the image surface side.

The fifth lens group G5 comprises a biconvex positive lens L51, acemented negative lens including a positive meniscus lens L52 having aconcave surface facing the object and a biconcave negative lens L53, acemented negative lens including a positive meniscus lens L54 having aconcave surface facing the object and a biconcave negative lens L55, anda parallel flat plate PP, which are arranged in order from the objectside. The positive meniscus lens L54 has an aspherical surface on theobject side.

Table 5 shows values of various data on the optical system according tothe Example 5.

TABLE 5 [General Data] f = 34.000 FNo = 1.23 ω = 32.2° Y = 21.7 TL =150.032 BF = 14.698 BFa (Air equivalent length) = 14.153 [Lens Data]Surface Number R D nd νd Object ∞ Surface 1 76.13006 3.000 1.48749 70.32 28.19692 7.115 3 45.00000 2.500 1.48749 70.3 4 26.27934 4.321 1.9459418.0 5 30.02901 12.043 6 −65.43865 1.800 1.67270 32.2 7 58.22961 9.8281.95375 32.3 8 −67.75158 Variable (D8) 9 −41.64169 1.800 1.80301 25.510* −102.52647 1.333 11 123.19210 9.223 1.59349 67.0 12 −48.08539Variable (D12) 13 −59.34145 4.766 1.49782 82.6 14 −38.44313 1.500 15 ST4.305 16 −70.75074 1.800 1.73800 32.3 17 32.10291 12.000 1.74310 49.418* −67.58277 0.200 19 54.42040 11.512 1.49782 82.6 20 −44.94038Variable (D20) 21 −89.95457 1.800 1.68893 31.2 22* 37.28507 Variable(D22) 23 48.04763 7.028 1.94594 18.0 24 −94.79098 0.200 25 −1608.554106.876 1.84850 43.8 26 −33.12297 1.800 1.75520 27.6 27 46.90755 4.956 28*−1000.00000 1.778 1.88202 37.2 29 −69.56777 1.800 1.68893 31.2 30126.27453 12.098 31 0 1.600 1.51680 64.1 32 0 (D32) Image ∞ Surface[Aspherical Surface Data] 10th Surface K = 1.0000 A4 = 3.07931E−06, A6 =1.02113E−09, A8 = 6.79561E−13, A10 = l.34649E−15 18th Surface K = 1.0000A4 = 5.15405E−06, A6 = 3.35051E−10, A8 = 4.01187E−12, A10 = l.76325E−1522nd Surface K = 0.0000 A4 = −1.84764E−06, A6 = 4.29577E−09, A8 =−1.18420E−11, A10 = l.99488E−14 28th Surface K = 1.0000 A4 =−1.23474E−05, A6 = −1.08882E−08, A8 = −1.46450E−11, A10 = −3.75662E−14[Lens Group Data] First Focal Magnification Magnification Group surfacelength (Infinity) (Short-distance) 1 1 −1313.18 0 1.10204 2 9 144.94−0.09157 −1.13582 3 13 38.77 0.20953 0.11808 4 21 −38.04 3.10241 2.997975 23 63.28 0.43496 0.43496 [Variable Distance Data] InfinityShort-distance f = 34.000 β = −0.1927 D0 ∞ 150.03 D8 11.884 3.852 D121.000 9.032 D20 1.000 4.973 D22 6.166 2.193 D32 1.000 1.000 [ Secondlens group Cofiguration Data] Focal length R1 R2 First −88.48936−41.64169 −102.52647 lens (9th Surface) (10th Surface) Second 59.46773123.19210 −48.08539 lens (11th Surface) (12th Surface)[Air Lens Data]Rear Group Air Convex Lens

R1=46.90755 (27th Surface), R2=−1000 (28th Surface), ShapeFactor=0.910388362

FIGS. 10A and 10B show various aberration values of the optical systemaccording to the Example 5 upon focusing on an infinity object and uponfocusing on a short distant object, respectively. From each aberrationdiagram, it can be seen that the optical system according to the Example5 excellently corrects various aberrations and has excellent imageformation performance.

Example 6

Example 6 will be described with reference to FIG. 11 , FIGS. 12A and12B, and Table 6.

FIG. 11 is a diagram showing a lens configuration of an optical systemaccording to the Example 6. A variable power optical system ZL (6)according to the Example 6 comprises a first lens group G1 havingpositive refractive power, a second lens group G2 (first focusing lensgroup) having positive refractive power, a third lens group G3(intermediate lens group) having positive refractive power, an aperturestop S arranged in the third lens group G3, a fourth lens group G4(second focusing lens group) having negative refractive power, and afifth lens group G5 (rear lens group) having positive refractive power,which are arranged in order from the object side. A front lens groupcomprises the first lens group G1 and the second lens group G2.

The positions of the first lens group G1, the third lens group G3, andthe fifth lens group G5 are fixed, and the second lens group G2 and thefourth lens group G4 are arranged so as to be movable along an opticalaxis. Upon focusing from infinity onto a short distance, the second lensgroup G2 moves in a direction to an object, and the fourth lens group G4moves in a direction to an image surface.

The first lens group G1 comprises a negative meniscus lens L11 having aconvex surface facing an object, a cemented negative lens including abiconcave negative lens L12 and a positive meniscus lens L13 having aconvex surface facing the object, and a biconvex positive lens L14,which are arranged in order from the object side.

The second lens group G2 comprises a negative meniscus lens L21 having aconcave surface facing the object, and a biconvex positive lens L22,which are arranged in order from the object side. The negative meniscuslens L21 has an aspherical surface on the image surface side.

The third lens group G3 comprises a positive meniscus lens L31 having aconcave surface facing the object, an aperture stop S, and a cementedpositive lens including a biconcave negative lens L32 and a biconvexpositive lens L33, which are arranged in order from the object side. Thepositive lens L33 has an aspherical surface on the image surface side.

The fourth lens group G4 comprises a biconcave negative lens L41. Thenegative lens L41 has an aspherical surface on the image surface side.

The fifth lens group G5 comprises a biconvex positive lens L51, abiconvex positive lens L52, a cemented negative lens including apositive meniscus lens L53 having a concave surface facing the objectand a biconcave negative lens L54, a cemented negative lens including abiconcave negative lens L55 and a biconvex positive lens L56, and aparallel flat plate PP, which are arranged in order from the objectside. The negative lens L55 has an aspherical surface on the objectside.

Table 6 shows values of various data on the optical system according tothe Example 6.

TABLE 6 [General Data] f = 34.000 FNo = 1.43 ω = 32.2° Y = 21.7 TL =125.022 BF = 13.600 BFa (Air equivalent length) = 13.055 [Lens Data]Surface Number R D nd νd Object ∞ Surface 1 109.45238 1.800 1.49700 81.62 24.47498 14.265 3 −78.28444 1.800 1.58144 41.0 4 40.43394 4.1661.94594 18.0 5 71.96151 0.425 6 83.61518 7.612 1.88300 40.7 7 −69.65237Variable (D7) 8 −39.56659 1.800 1.80301 25.5 9* −90.71735 0.563 1065.77353 9.415 1.59319 67.9 11 −45.93702 Variable (D11) 12 −138.843054.771 1.49782 82.6 13 −45.83784 1.500 14 ST 3.722 15 −59.21512 1.8001.75520 27.6 16 22.18297 11.699 1.85108 40.1 17* −46.92005 Variable(D17) 18 −67.56515 1.800 1.58887 61.1 19* 38.75771 Variable (D19) 2077.17615 3.123 1.59319 67.9 21 −218.81205 0.200 22 36.66031 8.3011.59319 67.9 23 −49.60222 0.200 24 −154.73327 3.307 1.94594 18.0 25−45.87169 1.800 1.65412 39.7 26 38.62341 5.378 27* −61.17607 1.8001.74310 49.4 28 672.86578 1.800 1.95375 32.3 29 −276.71080 11.000 300.00000 1.600 1.51680 64.1 31 0.00000 (D31) Image ∞ Surface [AsphericalSurface Data] 9th Surface K = 1.0000 A4 = 3.97662E−06, A6 = 1.92523E−09,A8 = 1.13694E−12, A10 = 3.88285E−15 17th Surface K = 1.0000 A4 =6.69227E−06, A6 = 8.04126E−10, A8 = 1.94276E−12, A10 = l.11930E−14 19thSurface K = 1.0000 A4 = −2.40528E−06, A6 = 1.93829E−09, A8 =−6.30888E−12, A10 = 6.60932E−14 27th Surface K = 1.0000 A4 =−2.15339E−05, A6 = −5.30707E−09, A8 = −1.26032E−10, A10 = l.30698E−13[Lens Group Data] First Focal Magnification Magnification Group surfacelength (Infinity) (Short-distance) 1 1 1823.66 0 1.58128 2 8 87.690.03453 −0.25825 3 12 58.66 0.44915 0.38745 4 18 −41.56 3.44727 3.351965 20 54.64 0.34870 0.34870 [Variable Distance Data] InfinityShort-distance f = 34.000 β = −0.1849 D0 ∞ 175.07 D7 8.879 4.001 D111.000 5.878 D17 1.085 5.047 D19 7.413 3.451 D31 1.000 1.000 [ Secondlens group Cofiguration Data] Focal length R1 R2 First −88.77822−39.56659 −90.71735 lens (8th Surface) (9th Surface) Second 47.0730465.77353 −45.93702 lens (11th Surface) (12th Surface)[Air Lens Data]Rear Group Air Convex Lens

R1=38.62341 (26th Surface), R2=−61.17607 (27th Surface), ShapeFactor=0.225979735

FIGS. 12A and 12B show various aberration values of the optical systemaccording to the Example 6 upon focusing on an infinity object and uponfocusing on a short distant object, respectively. From each aberrationdiagram, it can be seen that the optical system according to the Example6 excellently corrects various aberrations and has excellent imageformation performance.

Example 7

Example 7 will be described with reference to FIG. 13 , FIGS. 14A and14B, and Table 7.

FIG. 13 is a diagram showing a lens configuration of an optical systemaccording to Example 7. A variable power optical system ZL (7) accordingto the Example 7 comprises a first lens group G1 having positiverefractive power, a second lens group G2 (first focusing lens group)having positive refractive power, a third lens group G3 (intermediatelens group) having positive refractive power, an aperture stop Sarranged in the third lens group G3, a fourth lens group G4 (secondfocusing lens group) having negative refractive power, and a fifth lensgroup G5 (rear lens group) having positive refractive power, which arearranged in order from the object side. A front lens group comprises thefirst lens group G1 and the second lens group G2.

The positions of the first lens group G1, the third lens group G3, andthe fifth lens group G5 are fixed, and the second lens group G2 and thefourth lens group G4 are arranged so as to be movable along an opticalaxis. Upon focusing from infinity onto a short distance, the second lensgroup G2 moves in a direction to an object, and the fourth lens group G4moves in a direction to an image surface.

The first lens group G1 comprises a negative meniscus lens L11 having aconvex surface facing the object, a cemented negative lens including abiconcave negative lens L12 and a positive meniscus lens L13 having aconvex surface facing the object, and a biconvex positive lens L14,which are arranged in order from the object side.

The second lens group G2 comprises a negative meniscus lens L21 having aconcave surface facing the object, and a biconvex positive lens L22,which are arranged in order from the object side. The negative meniscuslens L21 has an aspherical surface on the image surface side. Thepositive lens L22 has an aspherical surface on the image surface side.

The third lens group G3 comprises a biconcave negative lens L31, anaperture stop S, and a cemented positive lens including a biconcavenegative lens L32 and a biconvex positive lens L33, which are arrangedin order from the object side. The positive lens L33 has an asphericalsurface on the image surface side.

The fourth lens group G4 comprises a biconcave negative lens L41, and apositive meniscus lens L42 having a convex surface facing the object,which are arranged in order from the object side.

The fifth lens group G5 comprises a biconvex positive lens L51, apositive meniscus lens L52 having a concave surface facing the object, acemented negative lens including a positive meniscus lens L53 having aconvex surface facing the object and a negative meniscus lens L54 havinga convex surface facing the object, a cemented negative lens including abiconcave negative lens L55 and a biconvex positive lens L56, and aparallel flat plate PP, which are arranged in order from the objectside. The positive lens L51 has an aspherical surface on the objectside.

Table 7 shows values of various data on the optical system according tothe Example 7.

TABLE 7 [General Data] f = 34.000 FNo = 1.43 ω = 33.0° Y = 21.7 TL =125.023 BF = 13.600 BFa (Air equivalent length) = 13.055 [Lens Data]Surface Number R D nd νd Object ∞ Surface 1 273.13198 1.800 1.49782 82.62 26.63571 13.925 3 −98.52314 1.800 1.48749 70.3 4 58.60262 3.1521.94594 18.0 5 101.66252 3.142 6 53.75225 10.436 1.75500 52.3 7−71.61260 Variable (D7) 8 −45.10806 1.800 1.80301 25.5 9* −116.808560.200 10 47.22397 10.971 11* −40.13400 Variable (D11) 12 −1586.662601.800 1.72825 28.4 13 68.71244 3.086 14 ST 3.025 15 −68.57829 1.8001.73800 32.3 16 20.10969 12.000 1.74310 49.4 17* −33.24316 Variable(D17) 18 −59.11057 1.800 1.73800 32.3 19 46.22177 0.241 20 45.598861.881 1.94594 18.0 21 70.00265 Variable (D21) 22* 47.37733 7.186 1.8820237.2 23 −49.42639 0.200 24 −64.96238 3.324 1.49782 82.6 25 −40.206500.200 26 101.56843 1.800 1.88300 40.7 27 209.60218 1.800 1.61266 44.5 2824.65699 7.101 29 −50.06935 1.800 1.55298 55.1 30 360.47016 1.8001.95375 32.3 31 −492.61890 11.000 32 0 1.600 1.51680 64.1 33 0 (D33)Image ∞ Surface [Aspherical Surface Data] 9th Surface K = 1.0000 A4 =3.85233E−06, A6 = −3.31696E−10, A8 = 1.06184E−13, A10 = −6.34887E−1511th Surface K = 1.0000 A4 = 3.77821E−06, A6 = 2.86601E−09, A8 =−2.15078E −12, A10 = 4.16703E−15 17th Surface K = 1.0000 A4 =1.14653E−05, A6 = 3.35768E−10, A8 = 2.01141E−11, A10 = −1.03562E−15 22ndSurface K = 1.0000 A4 = −5.47144E−06, A6 = −7.00429E−09, A8 =1.65756E−11, A10 = −1.71978E−14 [Lens Group Data] First FocalMagnification Magnification Group surface length (Infinity)(Short-distance) 1 1 113.48 0 −1.00482 2 8 59.44 0.29513 0.18580 3 12180.29 1.03982 1.02781 4 18 −46.77 3.97828 3.92885 5 22 46.19 0.245410.24541 [Variable Distance Data] Infinity Short-distance f = 34.000 β =−0.1850 D0 ∞ 175.05 D7 8.039 3.567 D11 1.000 5.472 D17 1.000 3.313 D213.313 1.000 D33 1.000 1.001 [Second lens group Cofiguration Data] Focallength R1 R2 First −92.54837 −45.10806 −116.80856 lens (8th Surface)(9th Surface) Second 38.44280 47.22397 −40.13400 lens (10th Surface)(11th Surface)[Air Lens Data]Rear Group Air Convex Lens

R1=24.65699 (28th Surface), R2=−50.06935 (29th Surface), ShapeFactor=0.340072323

FIGS. 14A and 14B show various aberration values of the optical systemaccording to the Example 7 upon focusing on an infinity object and uponfocusing on a short distant object, respectively. From each aberrationdiagram, it can be seen that the optical system according to the Example7 excellently corrects various aberrations and has excellent imageformation performance.

Example 8

Example 8 will be described with reference to FIG. 15 , FIGS. 16A and16B, and Table 8.

FIG. 15 is a diagram showing a lens configuration of an optical systemaccording to the Example 8. A variable power optical system ZL (8)according to the Example 8 comprises a first lens group G1 (firstfocusing lens group) having positive refractive power, a second lensgroup G2 (intermediate lens group) having positive refractive power, anaperture stop S arranged in the second lens group G2, a third lens groupG3 (second focusing lens group) having negative refractive power, and afourth lens group G4 (rear lens group) having positive refractive power,which are arranged in order from the object side. A front lens groupcomprises the first lens group G1.

The positions of the second lens group G2 and the fourth lens group G4are fixed, and the first lens group G1 and the third lens group G3 arearranged to be movable along an optical axis. Upon focusing frominfinity onto a short distance, the first lens group G1 moves in adirection to an object, and the third lens group G3 moves in a directionto an image surface.

The first lens group G1 comprises a negative meniscus lens L11 having aconcave surface facing the object and a biconvex positive lens L12,which are arranged in order from the object side. The negative meniscuslens L11 has an aspherical surface on the image surface side. Thepositive lens L12 has an aspherical surface on the image surface side.

The second lens group G2 comprises a cemented negative lens including abiconcave negative lens L21 and a biconvex positive lens L22, anaperture stop S, and a biconvex positive lens L23, which are arranged inorder from the object side. The positive lens L23 is an asphericalsurface on the image surface side.

The third lens group G3 comprises a biconcave negative lens L31.

The fourth lens group G4 comprises a biconvex positive lens L41, anegative meniscus lens L42 having a convex surface facing the object, acemented positive lens including a biconvex positive lens L43 and abiconcave negative lens L44, a cemented negative lens including abiconcave negative lens L45 and a biconvex positive lens L46, and aparallel flat plate PP, which are arranged in order from the objectside. The positive lens L46 has an aspherical surface on the imagesurface side.

Table 8 shows values of various data on the optical system according tothe Example 8.

TABLE 8 [General Data] f = 50.910 FNo = 1.43 m = 22.8° Y = 21.7 TL =95.871 BF = 16.056 BFa (Air equivalent length) = 15.510 [Lens Data]Surface Number R D nd νd Object ∞ Surface 1 −45.53128 2.000 1.80301 25.52* −111.79675 0.200 3 83.73710 12.000 1.59201 67.0 4* −49.75520 Variable(D4) 5 −68.03249 1.800 1.73800 32.3 6 1749.28940 2.677 1.94594 18.0 7−155.93999 1.500 8 ST 4.123 9 71.59071 7.854 1.49710 81.5 10* −54.23941Variable (D10) 11 −219.41482 1.800 1.48749 70.3 12 39.44184 Variable(D12) 13 47.97944 9.342 1.88300 40.7 14 −135.75041 0.200 15 545.978951.800 1.61266 44.5 16 23.28740 0.200 17 23.74117 9.978 1.84850 43.8 18−29.27432 1.800 1.73800 32.3 19 26.87419 5.111 20 −34.55237 1.8001.84666 23.8 21 406.87881 2.828 1.74310 49.4 22* −48.46023 13.455 23 01.600 1.51680 64.1 24 0 (D24) Image ∞ Surface [Aspherical Surface Data]2nd Surface K = 1.0000 A4 = 3.11319E−06, A6 = 1.64862E−10, A8 =2.89903E−13, A10 = 1.18346E−15 4th Surface K = 1.0000 A4 = −1.09516E−06,A6 = 2 .90379E−09, A8 = −4.49476E−12, A10 = 2.65768E−15 10th Surface K =1.0000 A4 = 3.59763E−06, A6 = −2 . 76589E−09, A8 = 6.50200E−12, A10 =−5.25418E−15 22nd Surface K = 1.0000 A4 = 1.20392E−05, A6 = 9.97149E−09, A8 = 5.72997E−11, A10 = −1.32184E−14 [Lens Group Data] FirstFocal Magnification Magnification Group surface length (Infinity)(Short-distance) 1 1 107.04 0 −0.54706 2 5 81.32 0.45966 0.36636 3 11−68.42 2.90838 2.78708 4 13 78.85 0.35580 0.35530 [Variable DistanceData] Infinity Short-distance f = 50.910 P = −0.1985 D0 ∞ 289.75 D41.000 14.500 D10 1.000 9.611 D12 10.802 2.191 D24 1.001 1.040 [Firstlens group Cofiguration Data] Focal length R1 R2 First lens −96.96346−45.53128 −111.79675 (1st Surface) (2nd Surface) Second lens 54.5427383.73710 −49.75520 (3rd Surface) (4th Surface)[Air Lens Data]Rear Group Air Convex Lens

R1=26.87419 (19th Surface), R2=−34.55237 (20th Surface), ShapeFactor=0.124997721

FIGS. 16A and 16B show various aberration values of the optical systemaccording to the Example 8 upon focusing on an infinity object and uponfocusing on a short distant object, respectively. From each aberrationdiagram, it can be seen that the optical system according to the Example8 excellently corrects various aberrations and has excellent imageformation performance.

The following shows a list of conditional expressions and conditionalexpression corresponding values of the respective examples.

[List of Conditional Expressions]βF1/βF2  (1)fF1/fF2  (2)(−MVF1)/MVF  (3)fF1/f  (4)fF2/f  (5)βF1  (6)1/βF2  (7){βF1+(1/βF1)}⁻²  (8){βF2+(1/βF2)}⁻²  (9)(−fM)/f  (10)fR/f  (11)fF2/fR  (12)−(r2Lm+r1Lm)/(r2Lm−r1Lm)  (13)(r2Lp+r1Lp)/(r2Lp−r1Lp)  (14)NAm/NAi  (15)(r2L1+r1L1)/(r2L1−r1L1)  (16)(r2Lr+r1Lr)/(r2Lr−r1Lr)  (17)2ω°)  (18)BFa/f  (19)

Conditional Expression Corresponding Values

Example 1 Example 2 Example 3 Example 4 (1) −0.0986 0.0024 −0.0128−0.0527 (2) 2.0165 0.8302 1.1938 2.1809 (3) 1.1483 6.5324 2.4310 2.6995(4) 3.2371 2.0682 2.5868 3.4459 (5) 1.6053 2.4912 2.1668 1.5800 (6)−1.2952 0.2870 0.2909 0.2363 (7) 0.0762 0.0082 −0.0441 −0.2230 (8)0.2340 0.0703 0.0719 0.0501 (9) 0.0057 6.76E−5 0.0019 0.0451 (10) 1.01090.8382 0.9050 0.9932 (11) 1.4600 1.3006 1.3838 2.0838 (12) 1.0995 1.91541.5658 0.7582 (13) 0.1944 0.9906 0.9273 0.3591 (14) 0.5184 0.1209 0.13150.1103 (15) 1.117 1.056 1.089 1.147 (16) — — — — (17) — — — — (18) 63.664.6 64.6 64.6 (19) 0.4391 0.4162 0.4357 0.6414 Example 5 Example 6Example 7 Example 8 (1) −0.0295 0.0100 0.0742 0 (2) −3.8102 −2.1100−1.2709 −1.5645 (3) 2.0216 1.2312 1.9334 1.5678 (4) 4.2629 2.5791 1.74822.1025 (5) −1.1188 −1.2224 −1.3756 −1.3439 (6) −0.0916 0.0345 0.2951 0(7) 0.3223 0.2901 0.2513 0.3438 (8) 0.0082 0.0012 0.0737 0 (9) 0.08530.0716 0.0559 0.0945 (10) −1.1403 −1.7253 −5.3026 −1.5973 (11) 1.86121.6071 1.3585 1.5488 (12) −0.6011 −0.7606 −1.0126 −0.8677 (13) — — — —(14) — — — — (15) — — — — (16) 2.3679 2.5471 2.2582 2.3742 (17) 0.91040.2260 0.3401 0.1250 (18) 64.4 64.4 66.0 45.6 (19) 0.4163 0.3840 0.38400.3047

According to each of the above-described examples, by reducing the sizeand weight of the focusing lens groups, it is possible to achieve anoptical system that can realize high-speed AF and quietness during AFwithout increasing the size of the lens barrel, and excellently suppressaberration fluctuations upon focusing from an infinity object onto ashort distant object.

The invention of the present application is not limited to the aboveembodiment, and can be appropriately modified as long as the opticalperformance specified by the recitations in Claims is not impaired. Ineach of the above examples, the four-group configuration and thefive-group configuration are shown, but the invention of the presentapplication may have other group configurations. For example, theinvention of the present application may be configured so that a lens ora lens group are added at a position closest to the object or the imagesurface in the optical system of each of the above examples. Here, thelens group is a portion having at least one lens which is separated withan air distance that changes upon focusing.

Further, any of a spherical surface, a flat surface, and an asphericalsurface may be adopted as the lens surface of the lens constituting theoptical system of the present application. The lens surface having aspherical surface or a flat surface has advantageous that lensprocessing and assembly adjustment are facilitated, deterioration ofoptical performance caused by errors in lens processing and assemblyadjustment can be prevented, and deterioration in depiction performanceis less even if the image surface shifts. The lens surface having anaspherical surface may be an aspherical surface obtained by grinding, aglass mold aspherical surface formed by molding glass into an asphericalshape with a mold, or a composite type aspherical surface formed byforming a resin provided on the glass surface into an aspherical shape.Further, the lens surface may be a diffraction surface, and the lens maybe a refractive index distribution type lens (GRIN lens) or a plasticlens.

Further, the lens surface of the lens constituting the optical system ofthe present application may be provided with an antireflection filmhaving a high transmittance in a wide wavelength range. As a result,flare and ghost can be reduced, and high-contrast and high opticalperformance can be achieved.

EXPLANATION OF NUMERALS AND CHARACTERS

-   G1 first lens group-   G2 second lens group-   G3 third lens group-   G4 fourth lens group-   G5 fifth lens group-   I image surface-   S aperture stop

The invention claimed is:
 1. An optical system consisting of a pluralityof lens groups including a first focusing lens group and a secondfocusing lens group which are arranged along an optical axis, whereinthe second focusing lens group is provided at a position closer to animage surface than the first focusing lens group, the first focusinglens group moves in a direction to an object along the optical axis uponfocusing on from an infinity object to a short distant object, thesecond focusing lens group moves in a direction to an image surfacealong the optical axis upon focusing on from an infinity object to ashort distant object, and the following conditional expression issatisfied:−0.20<βF1/βF2<0.50, where βF1: a lateral magnification of the firstfocusing lens group upon focusing on the infinity object, and βF2: alateral magnification of the second focusing lens group upon focusing onthe infinity object.
 2. The optical system according to claim 1, whereinthe following conditional expression is satisfied:−4.50<fF1/fF2<3.00, where fF1: a focal length of the first focusing lensgroup, and fF2: a focal length of the second focusing lens group.
 3. Theoptical system according to claim 1, wherein the following conditionalexpression is satisfied:0.50<(−MVF1)/MVF2<7.00, where MVF1: a movement amount of the firstfocusing lens group upon focusing from the infinity object onto theshort distant object, and MVF2: a movement amount of the second focusinglens group upon focusing from the infinity object onto the short distantobject (the movement amounts represent movements in the direction to theimage surface with positive values).
 4. The optical system according toclaim 1, wherein the following conditional expression is satisfied:1.30<fF1/f<5.00, where fF1: a focal length of the first focusing lensgroup, and f: a focal length of the entire optical system.
 5. Theoptical system according to claim 1, wherein the following conditionalexpression is satisfied:−2.00<fF2/f<−0.05, or 0.05<fF2/f<3.00, where fF2: a focal length of thesecond focusing lens group, and f: a focal length of the entire opticalsystem.
 6. The optical system according to claim 1, wherein thefollowing conditional expression is satisfied:−1.80<βF1<0.60, where βF1: the lateral magnification of the firstfocusing lens group upon focusing on the infinity object.
 7. The opticalsystem according to claim 1, wherein the following conditionalexpression is satisfied:−0.60<1/βF2<0.70, where βF2: the lateral magnification of the secondfocusing lens group upon focusing on the infinity object.
 8. The opticalsystem according to claim 1, wherein the following conditionalexpression is satisfied:{βF1+(1/βF1)}⁻²<0.250, where βF1: the lateral magnification of the firstfocusing lens group upon focusing on the infinity object.
 9. The opticalsystem according to claim 1, wherein the following conditionalexpression is satisfied:{βF2+(1/βF2)}⁻²<0.160, where βF2: the lateral magnification of thesecond focusing lens group upon focusing on the infinity object.
 10. Theoptical system according to claim 1, consisting of a front lens groupincluding the first focusing lens group, an intermediate lens group, thesecond focusing lens group, and a rear lens group having positiverefractive power, which are arranged in this order closest to theobject, wherein the first focusing lens group is arranged at a positionclosest to the image surface in the front lens group.
 11. The opticalsystem according to claim 1, consisting of a front lens group includingthe first focusing lens group, an intermediate lens group, the secondfocusing lens group, and a rear lens group having positive refractivepower, which are arranged in this order closest to the object, whereinthe intermediate lens group and the second focusing lens group havedifferent signs in refractive power.
 12. The optical system according toclaim 1, further comprising an intermediate lens group to be arrangedbetween the first focusing lens group and the second focusing lensgroup, wherein the following conditional expression is satisfied:−8.00<(−fM)/f<2.00, where fM: a focal length of the intermediate lensgroup, and f: a focal length of the entire optical system.
 13. Theoptical system according to claim 1, further comprising a rear lensgroup which is arranged on the image surface side of the second focusinglens group and has positive refractive power, wherein the followingconditional expression is satisfied:0.50<fR/f<3.50, where fR: a focal length of the rear lens group, and f:a focal length of the entire optical system.
 14. The optical systemaccording to claim 1, further comprising a rear lens group which isarranged on the image surface side of the second focusing lens group andhas positive refractive power, wherein the following conditionalexpression is satisfied:−2.00<fF2/fR<3.00, where fF2: a focal length of the second focusing lensgroup, and fR: a focal length of the rear lens group.
 15. The opticalsystem according to claim 1, wherein a lens arranged at a positionclosest to the object is a negative meniscus lens.
 16. The opticalsystem according to claim 1, further comprising an intermediate lensgroup to be arranged between the first focusing lens group and thesecond focusing lens group, wherein the intermediate lens group isconfigured so that at least one air lens having positive refractivepower is formed, and the following conditional expression is satisfied:0.10<−(r2Lm+r1Lm)/(r2Lm−r1Lm)<1.20, where r1Lm: a radius of curvature ofa surface on an object side of an air lens closest to the image surfaceamong air lenses formed in the intermediate lens group, and r2Lm: aradius of curvature of a surface on an image surface side of an air lensclosest to the image surface among the air lenses formed in theintermediate lens group.
 17. The optical system according to claim 1,further comprising a leading lens group arranged on the object side ofthe first focusing lens group, wherein the leading lens group includes anegative meniscus lens and a negative lens arranged in this orderclosest to the object, an air lens is formed between the negativemeniscus lens and the negative lens, and the following conditionalexpression is satisfied:0<(r2Lp+r1Lp)/(r2Lp−r1Lp)<1.20, where r1Lp: a radius of curvature of asurface on the object side of the air lens formed in the leading lensgroup, and r2Lp: a radius of curvature of a surface on the image surfaceside of the air lens formed in the leading lens group.
 18. The opticalsystem according to claim 1, wherein the following conditionalexpression is satisfied:1.00<NAm/NAi<1.50, where NAi: a numerical aperture on the image sideupon focusing on the infinity object, and NAm: a numerical aperture onthe image side upon focusing on the short distant object.
 19. Theoptical system according to claim 1, wherein a lens arranged at aposition closest to the object among lenses constituting the firstfocusing lens group is a negative lens, and the following conditionalexpression is satisfied:1.50<(r2L1+r1L1)/(r2L1−r1L1)<3.50, where r1L1: a radius of curvature ofa surface on the object side of the negative lens, and r2L1: a radius ofcurvature of a surface on the image surface side of the negative lens.20. The optical system according to claim 1, further comprising a rearlens group which is arranged on the image surface side of the secondfocusing lens group and has positive refractive power, wherein the rearlens group is configured to form an air lens, and the followingconditional expression is satisfied:0.00<(r2Lr+r1Lr)/(r2Lr−r1Lr)<1.20, where r1Lr: a radius of curvature ofa surface on the object side of the air lens formed in the rear lensgroup, and r2Lr: a radius of curvature of a surface on the image surfaceside of the air lens formed in the rear lens group.
 21. The opticalsystem according to claim 1, wherein the following conditionalexpression is satisfied:25.00°<2ω<75.00°, where 2ω: a total angle of view of the optical system.22. The optical system according to claim 1, wherein the followingconditional expression is satisfied:0.10<BFa/f<0.75, where BFa: a back focus (air equivalent length) of theoptical system, and f: a focal length of the entire optical system. 23.An optical apparatus comprising the optical system according to claim 1.24. The optical system according to claim 1, wherein the first focusinglens group has positive refractive power.
 25. A method for manufacturingan optical system comprising: configuring each of a plurality of lensgroups including a first focusing lens group and a second focusing lensgroup: and arranging the configured lens groups in a lens barrel sothat; the first focusing lens group and the second focusing lens groupare arranged along an optical axis; the second focusing lens group isprovided at a position closer to an image surface than the firstfocusing lens group; the first focusing lens group has positiverefractive power and moves in a direction to an object along the opticalaxis upon focusing on from an infinity object to a short distant object;the second focusing lens group moves in a direction to an image surfacealong the optical axis upon focusing on from an infinity object to ashort distant object; and the first focusing lens group and the secondfocusing lens group satisfy the following conditional expression:−0.20<βF1/βF2<0.50, where βF1: a lateral magnification of the firstfocusing lens group, and βF2: a lateral magnification of the secondfocusing lens group.